Coordinated access point spatial reuse

ABSTRACT

This disclosure provides methods, devices and systems for sharing resources of a wireless medium. Various implementations relate generally to coordinated transmit power control for sharing time and frequency resources of a wireless medium. Particular implementations relate more specifically to coordinated access point spatial-reuse-multiple-access techniques for sharing the time and frequency resources of a transmission opportunity. According to such techniques, an access point that wins contention and gains access to the wireless medium for the duration of a transmission opportunity may limit the transmit powers of the access points selected to share the time and frequency resources such that interference from the selected access points does not prevent stations associated with the winning access point from successfully decoding packets transmitted by it.

PRIORITY INFORMATION

The present Application for Patent claims priority under 35 U.S.C. § 119to U.S. Provisional Patent Application No. 62/929,653 filed 1 Nov. 2019,entitled “COORDINATED ACCESS POINT SPATIAL REUSE,” which is assigned tothe assignee hereof and hereby expressly incorporated by referenceherein.

TECHNICAL FIELD

This disclosure relates generally to wireless communication, and morespecifically, to coordinated transmit power control for sharing the timeand frequency resources of a transmission opportunity.

DESCRIPTION OF THE RELATED TECHNOLOGY

A wireless local area network (WLAN) may be formed by one or more accesspoints (APs) that provide a shared wireless communication medium for useby a number of client devices also referred to as stations (STAs). Thebasic building block of a WLAN conforming to the Institute of Electricaland Electronics Engineers (IEEE) 802.11 family of standards is a BasicService Set (BSS), which is managed by an AP. Each BSS is identified bya Basic Service Set Identifier (BSSID) that is advertised by the AP. AnAP periodically broadcasts beacon frames to enable any STAs withinwireless range of the AP to establish or maintain a communication linkwith the WLAN.

Conventional access techniques involve contention. APs or STAs desiringto transmit or receive data must contend for access to the wirelessmedium and win the contention before obtaining a transmissionopportunity (TXOP) to transmit or receive data. However, conventionalaccess techniques may use the time or frequency resources of the TXOPinefficiently, which may lead to increased latency and reducedthroughput fairness.

SUMMARY

The systems, methods and devices of this disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosurecan be implemented in a method for wireless communication. The methodincludes obtaining a transmission opportunity for wireless communicationvia a wireless channel. The method also includes selecting one or moreother wireless access points to participate in the transmissionopportunity. The method also includes determining a maximum transmitpower permitted to be used by each of the one or more selected accesspoints for transmissions during the transmission opportunity. The methodadditionally includes transmitting a message to the one or more selectedaccess points that includes, for each of the selected access points: anindication of time and frequency resources of the transmissionopportunity usable by the selected access point to transmit data to, orreceive data from, one or more respective wireless stations associatedwith the access point during the transmission opportunity; and anindication of the maximum transmit power for the selected access point.The method further includes transmitting data to, or receiving datafrom, one or more first wireless stations associated with the firstwireless access point using the indicated time and frequency resources.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a wireless communication device. Thewireless communication device includes at least one modem, at least oneprocessor communicatively coupled with the at least one modem, and atleast one memory communicatively coupled with the at least one processorand storing processor-readable code that, when executed by the at leastone processor in conjunction with the at least one modem, is configuredto obtain a transmission opportunity for wireless communication via awireless channel. The code, when executed by the at least one processorin conjunction with the at least one modem, is also configured to selectone or more other wireless access points to participate in thetransmission opportunity. The code, when executed by the at least oneprocessor in conjunction with the at least one modem, is also configuredto determine a maximum transmit power permitted to be used by each ofthe one or more selected access points for transmissions during thetransmission opportunity. The code, when executed by the at least oneprocessor in conjunction with the at least one modem, is additionallyconfigured to transmit a message to the one or more selected accesspoints that includes, for each of the selected access points: anindication of time and frequency resources of the transmissionopportunity usable by the selected access point to transmit data to, orreceive data from, one or more respective wireless stations associatedwith the access point during the transmission opportunity; and anindication of the maximum transmit power for the access point. The code,when executed by the at least one processor in conjunction with the atleast one modem, is further configured to transmit data to, or receivedata from, one or more first wireless stations associated with the firstwireless access point using the indicated time and frequency resources.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method. The method includes receivinga first frame from at least one station associated with a secondwireless access point. The method also includes determining a receivedpower of the first frame. The method also includes transmitting a secondframe to the second wireless access point that includes a powerindication based on the received power. The method additionally includesreceiving a third frame from the second wireless access point thatincludes: an indication of time and frequency resources of atransmission opportunity usable by the first wireless access point totransmit data to, or receive data from, one or more wireless stationsassociated with the first wireless access point during the transmissionopportunity; and an indication of a maximum transmit power permitted tobe used by the first wireless access point for transmissions using thetime and frequency resources. The method further includes transmittingdata to, or receiving data from, one or more of the wireless stationsassociated with the first wireless access point using the indicated timeand frequency resources at a power at or below the indicated maximumtransmit power.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in a wireless communication device. Thewireless communication device includes at least one modem, at least oneprocessor communicatively coupled with the at least one modem, and atleast one memory communicatively coupled with the at least one processorand storing processor-readable code that, when executed by the at leastone processor in conjunction with the at least one modem, is configuredto receive a first frame from at least one station associated with asecond wireless access point. The code, when executed by the at leastone processor in conjunction with the at least one modem, is alsoconfigured to determine a received power of the first frame. The code,when executed by the at least one processor in conjunction with the atleast one modem, is also configured to transmit a second frame to thesecond wireless access point that includes a power indication based onthe received power. The code, when executed by the at least oneprocessor in conjunction with the at least one modem, is additionallyconfigured to receive a third frame from the second wireless accesspoint that includes: an indication of time and frequency resources of atransmission opportunity usable by the first wireless access point totransmit data to, or receive data from, one or more wireless stationsassociated with the first wireless access point during the transmissionopportunity; and an indication of a maximum transmit power permitted tobe used by the first wireless access point for transmissions using thetime and frequency resources. The code, when executed by the at leastone processor in conjunction with the at least one modem, is furtherconfigured to transmit data to, or receive data from, one or more of thewireless stations associated with the first wireless access point usingthe indicated time and frequency resources at a power at or below theindicated maximum transmit power.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of one or more implementations of the subject matter describedin this disclosure are set forth in the accompanying drawings and thedescription below. However, the accompanying drawings illustrate onlysome typical aspects of this disclosure and are therefore not to beconsidered limiting of its scope. Other features, aspects, andadvantages will become apparent from the description, the drawings andthe claims.

FIG. 1 shows a pictorial diagram of an example wireless communicationnetwork.

FIG. 2A shows an example protocol data unit (PDU) usable forcommunications between an access point (AP) and a number of stations(STAs).

FIG. 2B shows an example field in the PDU of FIG. 2A.

FIG. 3A shows an example PHY layer convergence protocol (PLCP) protocoldata unit (PPDU) usable for communications between an AP and one or moreSTAs.

FIG. 3B shows another example PPDU usable for communications between anAP and one or more STAs.

FIG. 4 shows a block diagram of an example wireless communicationdevice.

FIG. 5A shows a block diagram of an example AP.

FIG. 5B shows a block diagram of an example STA.

FIG. 6 shows a flowchart illustrating an example process for coordinatedwireless communication that supports resource sharing according to someimplementations.

FIG. 7 shows a timing diagram illustrating the transmissions ofcommunications in the example process of FIG. 6.

FIG. 8 shows a flowchart illustrating an example transmissionopportunity (TXOP) indication process for advertising an availability oftime and frequency resources in the TXOP.

FIG. 9 shows a flowchart illustrating an example schedule allocationprocess for allocating time and frequency resources in the TXOP.

FIG. 10 shows a flowchart illustrating an example process forcoordinated wireless communication that supports resource sharingaccording to some implementations.

FIG. 11 shows a block diagram of an example wireless communicationdevice that supports resource sharing according to some implementations.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following description is directed to some particular implementationsfor the purposes of describing innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations can be implemented in anydevice, system or network that is capable of transmitting and receivingradio frequency (RF) signals according to one or more of the Instituteof Electrical and Electronics Engineers (IEEE) 802.11 standards, theIEEE 802.15 standards, the Bluetooth® standards as defined by theBluetooth Special Interest Group (SIG), or the Long Term Evolution(LTE), 3G, 4G or 5G (New Radio (NR)) standards promulgated by the 3rdGeneration Partnership Project (3GPP), among others. The describedimplementations can be implemented in any device, system or network thatis capable of transmitting and receiving RF signals according to one ormore of the following technologies or techniques: code division multipleaccess (CDMA), time division multiple access (TDMA), frequency divisionmultiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA(SC-FDMA), single-user (SU) multiple-input multiple-output (MIMO) andmulti-user (MU) MIMO. The described implementations also can beimplemented using other wireless communication protocols or RF signalssuitable for use in one or more of a wireless personal area network(WPAN), a wireless local area network (WLAN), a wireless wide areanetwork (WWAN), or an internet of things (IOT) network.

Various implementations relate generally to coordinated transmit powercontrol for sharing time and frequency resources of a wireless medium.Particular implementations relate more specifically to coordinated AP(CAP) spatial-reuse-multiple-access (SRMA) techniques for sharing thetime and frequency resources of a transmission opportunity (TXOP).According to such techniques, an AP that wins contention and gainsaccess to the wireless medium for the duration of a TXOP (referred to asthe TXOP owner) may limit the transmit powers of the APs selected toshare the time and frequency resources such that interference from theselected APs does not prevent STAs associated with the TXOP owner fromsuccessfully decoding packets transmitted by the TXOP owner.

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. In some implementations, the described techniquescan be used to reduce latency because the TXOP owner may share a TXOPwith other APs, and as such, the other APs may not need to wait to wincontention for a TXOP to be able to transmit and receive data accordingto conventional CSMA/CA or EDCA techniques. Additionally oralternatively, some implementations can achieve improvements inthroughput fairness. Various implementations may achieve these and otheradvantages without requiring that the TXOP owner or the other APsselected to participate in the TXOP be aware of the STAs associated withother BSSs (OBSSs), without requiring a preassigned or dedicated masterAP or preassigned groups of APs, and without requiring backhaulcoordination between the APs participating in the TXOP.

FIG. 1 shows a block diagram of an example wireless communicationnetwork 100. According to some aspects, the wireless communicationnetwork 100 can be an example of a wireless local area network (WLAN)such as a Wi-Fi network (and will hereinafter be referred to as WLAN100). For example, the WLAN 100 can be a network implementing at leastone of the IEEE 802.11 family of wireless communication protocolstandards (such as that defined by the IEEE 802.11-2016 specification oramendments thereof including, but not limited to, 802.11 ay, 802.11ax,802.11az, 802.11ba and 802.11be). The WLAN 100 may include numerouswireless communication devices such as an access point (AP) 102 andmultiple stations (STAs) 104. While only one AP 102 is shown, the WLANnetwork 100 also can include multiple APs 102.

Each of the STAs 104 also may be referred to as a mobile station (MS), amobile device, a mobile handset, a wireless handset, an access terminal(AT), a user equipment (UE), a subscriber station (SS), or a subscriberunit, among other examples. The STAs 104 may represent various devicessuch as mobile phones, personal digital assistant (PDAs), other handhelddevices, netbooks, notebook computers, tablet computers, laptops,display devices (for example, TVs, computer monitors, navigationsystems, among others), music or other audio or stereo devices, remotecontrol devices (“remotes”), printers, kitchen or other householdappliances, key fobs (for example, for passive keyless entry and start(PKES) systems), among other examples.

A single AP 102 and an associated set of STAs 104 may be referred to asa basic service set (BSS), which is managed by the respective AP 102.FIG. 1 additionally shows an example coverage area 106 of the AP 102,which may represent a basic service area (BSA) of the WLAN 100. The BSSmay be identified to users by a service set identifier (SSID), as wellas to other devices by a basic service set identifier (BSSID), which maybe a medium access control (MAC) address of the AP 102. The AP 102periodically broadcasts beacon frames (“beacons”) including the BSSID toenable any STAs 104 within wireless range of the AP 102 to “associate”or re-associate with the AP 102 to establish a respective communicationlink 108 (hereinafter also referred to as a “Wi-Fi link”), or tomaintain a communication link 108, with the AP 102. For example, thebeacons can include an identification of a primary channel used by therespective AP 102 as well as a timing synchronization function forestablishing or maintaining timing synchronization with the AP 102. TheAP 102 may provide access to external networks to various STAs 104 inthe WLAN via respective communication links 108.

To establish a communication link 108 with an AP 102, each of the STAs104 is configured to perform passive or active scanning operations(“scans”) on frequency channels in one or more frequency bands (forexample, the 2.4 GHz, 5 GHz, 6 GHz or 60 GHz bands). To perform passivescanning, a STA 104 listens for beacons, which are transmitted byrespective APs 102 at a periodic time interval referred to as the targetbeacon transmission time (TBTT) (measured in time units (TUs) where oneTU may be equal to 1024 microseconds (μs)). To perform active scanning,a STA 104 generates and sequentially transmits probe requests on eachchannel to be scanned and listens for probe responses from APs 102. EachSTA 104 may be configured to identify or select an AP 102 with which toassociate based on the scanning information obtained through the passiveor active scans, and to perform authentication and associationoperations to establish a communication link 108 with the selected AP102. The AP 102 assigns an association identifier (AID) to the STA 104at the culmination of the association operations, which the AP 102 usesto track the STA 104.

As a result of the increasing ubiquity of wireless networks, a STA 104may have the opportunity to select one of many BSSs within range of theSTA or to select among multiple APs 102 that together form an extendedservice set (ESS) including multiple connected BSSs. An extended networkstation associated with the WLAN 100 may be connected to a wired orwireless distribution system that may allow multiple APs 102 to beconnected in such an ESS. As such, a STA 104 can be covered by more thanone AP 102 and can associate with different APs 102 at different timesfor different transmissions. Additionally, after association with an AP102, a STA 104 also may be configured to periodically scan itssurroundings to find a more suitable AP 102 with which to associate. Forexample, a STA 104 that is moving relative to its associated AP 102 mayperform a “roaming” scan to find another AP 102 having more desirablenetwork characteristics such as a greater received signal strengthindicator (RSSI) or a reduced traffic load.

In some cases, STAs 104 may form networks without APs 102 or otherequipment other than the STAs 104 themselves. One example of such anetwork is an ad hoc network (or wireless ad hoc network). Ad hocnetworks may alternatively be referred to as mesh networks orpeer-to-peer (P2P) networks. In some cases, ad hoc networks may beimplemented within a larger wireless network such as the WLAN 100. Insuch implementations, while the STAs 104 may be capable of communicatingwith each other through the AP 102 using communication links 108, STAs104 also can communicate directly with each other via direct wirelesslinks 110. Additionally, two STAs 104 may communicate via a directcommunication link 110 regardless of whether both STAs 104 areassociated with and served by the same AP 102. In such an ad hoc system,one or more of the STAs 104 may assume the role filled by the AP 102 ina BSS. Such a STA 104 may be referred to as a group owner (GO) and maycoordinate transmissions within the ad hoc network. Examples of directwireless links 110 include Wi-Fi Direct connections, connectionsestablished by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, andother P2P group connections.

The APs 102 and STAs 104 may function and communicate (via therespective communication links 108) according to the IEEE 802.11 familyof wireless communication protocol standards (such as that defined bythe IEEE 802.11-2016 specification or amendments thereof including, butnot limited to, 802.11 ay, 802.11ax, 802.11az, 802.11ba and 802.11be).These standards define the WLAN radio and baseband protocols for the PHYand medium access control (MAC) layers. The APs 102 and STAs 104transmit and receive wireless communications (hereinafter also referredto as “Wi-Fi communications”) to and from one another in the form of PHYprotocol data units (PPDUs) (or physical layer convergence protocol(PLCP) PDUs). The APs 102 and STAs 104 in the WLAN 100 may transmitPPDUs over an unlicensed spectrum, which may be a portion of spectrumthat includes frequency bands traditionally used by Wi-Fi technology,such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHzband, and the 900 MHz band. Some implementations of the APs 102 and STAs104 described herein also may communicate in other frequency bands, suchas the 6 GHz band, which may support both licensed and unlicensedcommunications. The APs 102 and STAs 104 also can be configured tocommunicate over other frequency bands such as shared licensed frequencybands, where multiple operators may have a license to operate in thesame or overlapping frequency band or bands.

Each of the frequency bands may include multiple sub-bands or frequencychannels. For example, PPDUs conforming to the IEEE 802.11n, 802.11ac,802.11ax and 802.11be standard amendments may be transmitted over the2.4, 5 GHz or 6 GHz bands, each of which is divided into multiple 20 MHzchannels. As such, these PPDUs are transmitted over a physical channelhaving a minimum bandwidth of 20 MHz, but larger channels can be formedthrough channel bonding. For example, PPDUs may be transmitted overphysical channels having bandwidths of 40 MHz, 80 MHz, 160 or 320 MHz bybonding together multiple 20 MHz channels.

Each PPDU is a composite structure that includes a PHY preamble and apayload in the form of a PHY service data unit (PSDU). The informationprovided in the preamble may be used by a receiving device to decode thesubsequent data in the PSDU. In instances in which PPDUs are transmittedover a bonded channel, the preamble fields may be duplicated andtransmitted in each of the multiple component channels. The PHY preamblemay include both a legacy portion (or “legacy preamble”) and anon-legacy portion (or “non-legacy preamble”). The legacy preamble maybe used for packet detection, automatic gain control and channelestimation, among other uses. The legacy preamble also may generally beused to maintain compatibility with legacy devices. The format of,coding of, and information provided in the non-legacy portion of thepreamble is based on the particular IEEE 802.11 protocol to be used totransmit the payload.

FIG. 2A shows an example protocol data unit (PDU) 200 usable forwireless communication between an AP and a number of STAs. For example,the PDU 200 can be configured as a PPDU. As shown, the PDU 200 includesa PHY preamble 202 and a PHY payload 204. For example, the preamble 202may include a legacy portion that itself includes a legacy shorttraining field (L-STF) 206, which may consist of two BPSK symbols, alegacy long training field (L-LTF) 208, which may consist of two BPSKsymbols, and a legacy signal field (L-SIG) 210, which may consist of twoBPSK symbols. The legacy portion of the preamble 202 may be configuredaccording to the IEEE 802.11a wireless communication protocol standard.The preamble 202 may also include a non-legacy portion including one ormore non-legacy fields 212, for example, conforming to an IEEE wirelesscommunication protocol such as the IEEE 802.11ac, 802.11ax, 802.11be orlater wireless communication protocol standards.

The L-STF 206 generally enables a receiving device to perform automaticgain control (AGC) and coarse timing and frequency estimation. The L-LTF208 generally enables a receiving device to perform fine timing andfrequency estimation and also to perform an initial estimate of thewireless channel. The L-SIG 210 generally enables a receiving device todetermine a duration of the PDU and to use the determined duration toavoid transmitting on top of the PDU. For example, the L-STF 206, theL-LTF 208 and the L-SIG 210 may be modulated according to a binary phaseshift keying (BPSK) modulation scheme. The payload 204 may be modulatedaccording to a BPSK modulation scheme, a quadrature BPSK (Q-BPSK)modulation scheme, a quadrature amplitude modulation (QAM) modulationscheme, or another appropriate modulation scheme. The payload 204 mayinclude a PSDU including a data field (DATA) 214 that, in turn, maycarry higher layer data, for example, in the form of medium accesscontrol (MAC) protocol data units (MPDUs) or an aggregated MPDU(A-MPDU).

FIG. 2B shows an example L-SIG 210 in the PDU 200 of FIG. 2A. The L-SIG210 includes a data rate field 222, a reserved bit 224, a length field226, a parity bit 228, and a tail field 230. The data rate field 222indicates a data rate (note that the data rate indicated in the datarate field 212 may not be the actual data rate of the data carried inthe payload 204). The length field 226 indicates a length of the packetin units of, for example, symbols or bytes. The parity bit 228 may beused to detect bit errors. The tail field 230 includes tail bits thatmay be used by the receiving device to terminate operation of a decoder(for example, a Viterbi decoder). The receiving device may utilize thedata rate and the length indicated in the data rate field 222 and thelength field 226 to determine a duration of the packet in units of, forexample, microseconds (μs) or other time units.

FIG. 3A shows an example PPDU 300 usable for wireless communicationbetween an AP and one or more STAs. The PPDU 300 may be used for SU,OFDMA or MU-MIMO transmissions. The PPDU 300 may be formatted as a HighEfficiency (HE) WLAN PPDU in accordance with the IEEE 802.11ax amendmentto the IEEE 802.11 wireless communication protocol standard. The PPDU300 includes a PHY preamble including a legacy portion 302 and anon-legacy portion 304. The PPDU 300 may further include a PHY payload306 after the preamble, for example, in the form of a PSDU including adata field 324.

The legacy portion 302 of the preamble includes an L-STF 308, an L-LTF310, and an L-SIG 312. The non-legacy portion 304 includes a repetitionof L-SIG (RL-SIG) 314, a first HE signal field (HE-SIG-A) 316, an HEshort training field (HE-STF) 320, and one or more HE long trainingfields (or symbols) (HE-LTFs) 322. For OFDMA or MU-MIMO communications,the second portion 304 further includes a second HE signal field(HE-SIG-B) 318 encoded separately from HE-SIG-A 316. HE-STF 320 may beused for timing and frequency tracking and AGC, and HE-LTF 322 may beused for more refined channel estimation. Like the L-STF 308, L-LTF 310,and L-SIG 312, the information in RL-SIG 314 and HE-SIG-A 316 may beduplicated and transmitted in each of the component 20 MHz channels ininstances involving the use of a bonded channel. In contrast, thecontent in HE-SIG-B 318 may be unique to each 20 MHz channel and targetspecific STAs 104.

RL-SIG 314 may indicate to HE-compatible STAs 104 that the PPDU 300 isan HE PPDU. An AP 102 may use HE-SIG-A 316 to identify and informmultiple STAs 104 that the AP has scheduled UL or DL resources for them.For example, HE-SIG-A 316 may include a resource allocation subfieldthat indicates resource allocations for the identified STAs 104.HE-SIG-A 316 may be decoded by each HE-compatible STA 104 served by theAP 102. For MU transmissions, HE-SIG-A 316 further includes informationusable by each identified STA 104 to decode an associated HE-SIG-B 318.For example, HE-SIG-A 316 may indicate the frame format, includinglocations and lengths of HE-SIG-Bs 318, available channel bandwidths andmodulation and coding schemes (MCSs), among other examples. HE-SIG-A 316also may include HE WLAN signaling information usable by STAs 104 otherthan the identified STAs 104.

HE-SIG-B 318 may carry STA-specific scheduling information such as, forexample, STA-specific (or “user-specific”) MCS values and STA-specificRU allocation information. In the context of DL MU-OFDMA, suchinformation enables the respective STAs 104 to identify and decodecorresponding resource units (RUs) in the associated data field 324.Each HE-SIG-B 318 includes a common field and at least one STA-specificfield. The common field can indicate RU allocations to multiple STAs 104including RU assignments in the frequency domain, indicate which RUs areallocated for MU-MIMO transmissions and which RUs correspond to MU-OFDMAtransmissions, and the number of users in allocations, among otherexamples. The common field may be encoded with common bits, CRC bits,and tail bits. The user-specific fields are assigned to particular STAs104 and may be used to schedule specific RUs and to indicate thescheduling to other WLAN devices. Each user-specific field may includemultiple user block fields. Each user block field may include two userfields that contain information for two respective STAs to decode theirrespective RU payloads in data field 324.

FIG. 3B shows another example PPDU 350 usable for wireless communicationbetween an AP and one or more STAs. The PPDU 350 may be used for SU,OFDMA or MU-MIMO transmissions. The PPDU 350 may be formatted as anExtreme High Throughput (EHT) WLAN PPDU in accordance with the IEEE802.11be amendment to the IEEE 802.11 wireless communication protocolstandard, or may be formatted as a PPDU conforming to any later(post-EHT) version of a new wireless communication protocol conformingto a future IEEE 802.11 wireless communication protocol standard orother wireless communication standard. The PPDU 350 includes a PHYpreamble including a legacy portion 352 and a non-legacy portion 354.The PPDU 350 may further include a PHY payload 356 after the preamble,for example, in the form of a PSDU including a data field 374.

The legacy portion 352 of the preamble includes an L-STF 358, an L-LTF360, and an L-SIG 362. The non-legacy portion 354 of the preambleincludes an RL-SIG 364 and multiple wireless communication protocolversion-dependent signal fields after RL-SIG 364. For example, thenon-legacy portion 354 may include a universal signal field 366(referred to herein as “U-SIG 366”) and an EHT signal field 368(referred to herein as “EHT-SIG 368”). One or both of U-SIG 366 andEHT-SIG 368 may be structured as, and carry version-dependentinformation for, other wireless communication protocol versions beyondEHT. The non-legacy portion 354 further includes an additional shorttraining field 370 (referred to herein as “EHT-STF 370,” although it maybe structured as, and carry version-dependent information for, otherwireless communication protocol versions beyond EHT) and one or moreadditional long training fields 372 (referred to herein as “EHT-LTFs372,” although they may be structured as, and carry version-dependentinformation for, other wireless communication protocol versions beyondEHT). EHT-STF 370 may be used for timing and frequency tracking and AGC,and EHT-LTF 372 may be used for more refined channel estimation. LikeL-STF 358, L-LTF 360, and L-SIG 362, the information in U-SIG 366 andEHT-SIG 368 may be duplicated and transmitted in each of the component20 MHz channels in instances involving the use of a bonded channel. Insome implementations, EHT-SIG 368 may additionally or alternativelycarry information in one or more non-primary 20 MHz channels that isdifferent than the information carried in the primary 20 MHz channel.

EHT-SIG 368 may include one or more jointly encoded symbols and may beencoded in a different block from the block in which U-SIG 366 isencoded. EHT-SIG 368 may be used by an AP to identify and informmultiple STAs 104 that the AP has scheduled UL or DL resources for them.EHT-SIG 368 may be decoded by each compatible STA 104 served by the AP102. EHT-SIG 368 may generally be used by a receiving device tointerpret bits in the data field 374. For example, EHT-SIG 368 mayinclude RU allocation information, spatial stream configurationinformation, and per-user signaling information such as MCSs, amongother examples. EHT-SIG 368 may further include a cyclic redundancycheck (CRC) (for example, four bits) and a tail (for example, 6 bits)that may be used for binary convolutional code (BCC). In someimplementations, EHT-SIG 368 may include one or more code blocks thateach include a CRC and a tail. In some aspects, each of the code blocksmay be encoded separately.

EHT-SIG 368 may carry STA-specific scheduling information such as, forexample, user-specific MCS values and user-specific RU allocationinformation. EHT-SIG 368 may generally be used by a receiving device tointerpret bits in the data field 374. In the context of DL MU-OFDMA,such information enables the respective STAs 104 to identify and decodecorresponding RUs in the associated data field 374. Each EHT-SIG 368 mayinclude a common field and at least one user-specific field. The commonfield can indicate RU distributions to multiple STAs 104, indicate theRU assignments in the frequency domain, indicate which RUs are allocatedfor MU-MIMO transmissions and which RUs correspond to MU-OFDMAtransmissions, and the number of users in allocations, among otherexamples. The common field may be encoded with common bits, CRC bits,and tail bits. The user-specific fields are assigned to particular STAs104 and may be used to schedule specific RUs and to indicate thescheduling to other WLAN devices. Each user-specific field may includemultiple user block fields. Each user block field may include, forexample, two user fields that contain information for two respectiveSTAs to decode their respective RU payloads.

The presence of RL-SIG 364 and U-SIG 366 may indicate to EHT- or laterversion-compliant STAs 104 that the PPDU 350 is an EHT PPDU or a PPDUconforming to any later (post-EHT) version of a new wirelesscommunication protocol conforming to a future IEEE 802.11 wirelesscommunication protocol standard. For example, U-SIG 366 may be used by areceiving device to interpret bits in one or more of EHT-SIG 368 or thedata field 374.

Access to the shared wireless medium is generally governed by adistributed coordination function (DCF). With a DCF, there is generallyno centralized master device allocating time and frequency resources ofthe shared wireless medium. On the contrary, before a wirelesscommunication device, such as an AP 102 or a STA 104, is permitted totransmit data, it must wait for a particular time and then contend foraccess to the wireless medium. In some implementations, the wirelesscommunication device may be configured to implement the DCF through theuse of carrier sense multiple access (CSMA) with collision avoidance(CA) (CSMA/CA) techniques and timing intervals. Before transmittingdata, the wireless communication device may perform a clear channelassessment (CCA) and determine that the appropriate wireless channel isidle. The CCA includes both physical (PHY-level) carrier sensing andvirtual (MAC-level) carrier sensing. Physical carrier sensing isaccomplished via a measurement of the received signal strength of avalid frame, which is then compared to a threshold to determine whetherthe channel is busy. For example, if the received signal strength of adetected preamble is above a threshold, the medium is considered busy.Physical carrier sensing also includes energy detection. Energydetection involves measuring the total energy the wireless communicationdevice receives regardless of whether the received signal represents avalid frame. If the total energy detected is above a threshold, themedium is considered busy. Virtual carrier sensing is accomplished viathe use of a network allocation vector (NAV), an indicator of a timewhen the medium may next become idle. The NAV is reset each time a validframe is received that is not addressed to the wireless communicationdevice. The NAV effectively serves as a time duration that must elapsebefore the wireless communication device may contend for access even inthe absence of a detected symbol or even if the detected energy is belowthe relevant threshold.

As described above, the DCF is implemented through the use of timeintervals. These time intervals include the slot time (or “slotinterval”) and the inter-frame space (IFS). The slot time is the basicunit of timing and may be determined based on one or more of atransmit-receive turnaround time, a channel sensing time, a propagationdelay and a MAC processing time. Measurements for channel sensing areperformed for each slot. All transmissions may begin at slot boundaries.Different varieties of IFS exist including the short IFS (SIFS), thedistributed IFS (DIFS), the extended IFS (EIFS), and the arbitration IFS(AIFS). For example, the DIFS may be defined as the sum of the SIFS andtwo times the slot time. The values for the slot time and IFS may beprovided by a suitable standard specification, such as one of the IEEE802.11 family of wireless communication protocol standards (such as thatdefined by the IEEE 802.11-2016 specification or amendments thereofincluding, but not limited to, 802.11ay, 802.11ax, 802.11az, 802.11baand 802.11be).

When the NAV reaches 0, the wireless communication device performs thephysical carrier sensing. If the channel remains idle for theappropriate IFS (for example, the DIFS), the wireless communicationdevice initiates a backoff timer, which represents a duration of timethat the device must sense the medium to be idle before it is permittedto transmit. The backoff timer is decremented by one slot each time themedium is sensed to be idle during a corresponding slot interval. If thechannel remains idle until the backoff timer expires, the wirelesscommunication device becomes the holder (or “owner”) of a transmitopportunity (TXOP) and may begin transmitting. The TXOP is the durationof time the wireless communication device can transmit frames over thechannel after it has won contention for the wireless medium. If, on theother hand, one or more of the carrier sense mechanisms indicate thatthe channel is busy, a MAC controller within the wireless communicationdevice will not permit transmission.

Each time the wireless communication devices generates a new PPDU fortransmission in a new TXOP, it randomly selects a new backoff timerduration. The available distribution of the numbers that may be randomlyselected for the backoff timer is referred to as the contention window(CW). If, when the backoff timer expires, the wireless communicationdevice transmits the PPDU, but the medium is still busy, there may be acollision. Additionally, if there is otherwise too much energy on thewireless channel resulting in a poor signal-to-noise ratio (SNR), thecommunication may be corrupted or otherwise not successfully received.In such instances, the wireless communication device may not receive acommunication acknowledging the transmitted PDU within a timeoutinterval. The MAC may then increase the CW exponentially, for example,doubling it, and randomly select a new backoff timer duration from theCW before each attempted retransmission of the PPDU. Before eachattempted retransmission, the wireless communication device may wait aduration of DIFS and, if the medium remains idle, then proceed toinitiate the new backoff timer. There are different CW and TXOPdurations for each of the four access categories (ACs): voice (AC_VO),video (AC_VI), background (AC_BK), and best effort (AC_BE). This enablesparticular types of traffic to be prioritized in the network.

As described above, APs 102 and STAs 104 can support multi-user (MU)communications; that is, concurrent transmissions from one device toeach of multiple devices (for example, multiple simultaneous downlink(DL) communications from an AP 102 to corresponding STAs 104), orconcurrent transmissions from multiple devices to a single device (forexample, multiple simultaneous uplink (UL) transmissions fromcorresponding STAs 104 to an AP 102). To support the MU transmissions,the APs 102 and STAs 104 may utilize multi-user multiple-input,multiple-output (MU-MIMO) and multi-user orthogonal frequency divisionmultiple access (MU-OFDMA) techniques.

In MU-OFDMA schemes, the available frequency spectrum of the wirelesschannel may be divided into multiple resource units (RUs) each includingmultiple frequency subcarriers (also referred to as “tones”). DifferentRUs may be allocated or assigned by an AP 102 to different STAs 104 atparticular times. The sizes and distributions of the RUs may be referredto as an RU allocation. In some implementations, RUs may be allocated in2 MHz intervals, and as such, the smallest RU may include 26 tonesconsisting of 24 data tones and 2 pilot tones. Consequently, in a 20 MHzchannel, up to 9 RUs (such as 2 MHz, 26-tone RUs) may be allocated(because some tones are reserved for other purposes). Similarly, in a160 MHz channel, up to 74 RUs may be allocated. Larger 52 tone, 106tone, 242 tone, 484 tone and 996 tone RUs may also be allocated.Adjacent RUs may be separated by a null subcarrier (such as a DCsubcarrier), for example, to reduce interference between adjacent RUs,to reduce receiver DC offset, and to avoid transmit center frequencyleakage.

For UL MU transmissions, an AP 102 can transmit a trigger frame toinitiate and synchronize an UL MU-OFDMA or UL MU-MIMO transmission frommultiple STAs 104 to the AP 102. Such trigger frames may thus enablemultiple STAs 104 to send UL traffic to the AP 102 concurrently in time.A trigger frame may address one or more STAs 104 through respectiveassociation identifiers (AIDs), and may assign each AID (and thus eachSTA 104) one or more RUs that can be used to send UL traffic to the AP102. The AP also may designate one or more random access (RA) RUs thatunscheduled STAs 104 may contend for.

As described above, APs 102 and STAs 104 can support multi-user (MU)communications; that is, concurrent transmissions from one device toeach of multiple devices (for example, multiple simultaneous downlink(DL) communications from an AP 102 to corresponding STAs 104), orconcurrent transmissions from multiple devices to a single device (forexample, multiple simultaneous uplink (UL) transmissions fromcorresponding STAs 104 to an AP 102). To support the MU transmissions,the APs 102 and STAs 104 may utilize multi-user multiple-input,multiple-output (MU-MIMO) and multi-user orthogonal frequency divisionmultiple access (MU-OFDMA) techniques.

In MU-OFDMA schemes, the available frequency spectrum of the wirelesschannel may be divided into multiple resource units (RUs) each includinga number of different frequency subcarriers (“tones”). Different RUs maybe allocated or assigned by an AP 102 to different STAs 104 atparticular times. The sizes and distributions of the RUs may be referredto as an RU allocation. In some implementations, RUs may be allocated in2 MHz intervals, and as such, the smallest RU may include 26 tonesconsisting of 24 data tones and 2 pilot tones. Consequently, in a 20 MHzchannel, up to 9 RUs (such as 2 MHz, 26-tone RUs) may be allocated(because some tones are reserved for other purposes). Similarly, in a160 MHz channel, up to 74 RUs may be allocated. Larger 52 tone, 106tone, 242 tone, 484 tone and 996 tone RUs may also be allocated.Adjacent RUs may be separated by a null subcarrier (such as a DCsubcarrier), for example, to reduce interference between adjacent RUs,to reduce receiver DC offset, and to avoid transmit center frequencyleakage.

For UL MU transmissions, an AP 102 can transmit a trigger frame toinitiate and synchronize an UL MU-OFDMA or UL MU-MIMO transmission frommultiple STAs 104 to the AP 102. Such trigger frames may thus enablemultiple STAs 104 to send UL traffic to the AP 102 concurrently in time.A trigger frame may address one or more STAs 104 through respectiveassociation identifiers (AIDs), and may assign each AID (and thus eachSTA 104) one or more RUs that can be used to send UL traffic to the AP102. The AP also may designate one or more random access (RA) RUs thatunscheduled STAs 104 may contend for.

Access to the shared wireless medium is generally governed by adistributed coordination function (DCF). With a DCF, there is generallyno centralized master device allocating time and frequency resources ofthe shared wireless medium. On the contrary, before a wirelesscommunication device, such as an AP 102 or a STA 104, is permitted totransmit data, it must wait for a particular time and then contend foraccess to the wireless medium. In some implementations, the wirelesscommunication device may be configured to implement the DCF through theuse of carrier sense multiple access (CSMA) with collision avoidance(CA) (CSMA/CA) techniques and timing intervals. Before transmittingdata, the wireless communication device may perform a clear channelassessment (CCA) and determine that the appropriate wireless channel isidle. The CCA may include both physical (PHY-level) carrier sensing andvirtual (MAC-level) carrier sensing. Physical carrier sensing isaccomplished via a measurement of the received signal strength of avalid frame, which is then compared to a threshold to determine whetherthe channel is busy. For example, if the received signal strength of adetected preamble is above a threshold, the medium is considered busy.Physical carrier sensing also includes energy detection. Energydetection involves measuring the total energy the wireless communicationdevice receives regardless of whether the received signal represents avalid frame. If the total energy detected is above a threshold, themedium is considered busy. Virtual carrier sensing is accomplished viathe use of a network allocation vector (NAV), an indicator of a timewhen the medium may next become idle. The NAV is reset each time a validframe is received that is not addressed to the wireless communicationdevice. The NAV effectively serves as a time duration that must elapsebefore the wireless communication device may contend for access even inthe absence of a detected symbol or even if the detected energy is belowthe relevant threshold.

As described above, the DCF is implemented through the use of timeintervals. These time intervals include the slot time (or “slotinterval”) and the inter-frame space (IFS). The slot time is the basicunit of timing and may be determined based on one or more of atransmit-receive turnaround time, a channel sensing time, a propagationdelay and a MAC processing time. Measurements for channel sensing areperformed for each slot. All transmissions may begin at slot boundaries.Different varieties of IFS exist including the short IFS (SIFS), thedistributed IFS (DIFS), the extended IFS (EIFS), and the arbitration IFS(AIFS). For example, the DIFS may be defined as the sum of the SIFS andtwo times the slot time. The values for the slot time and IFS may beprovided by a suitable standard specification, such as one of the IEEE802.11 family of wireless communication protocol standards (such as thatdefined by the IEEE 802.11-2016 specification or amendments thereofincluding, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax,802.11az, 802.11ba and 802.11be).

When the NAV reaches 0, the wireless communication device performs thephysical carrier sensing. If the channel remains idle for theappropriate IFS (for example, the DIFS), the wireless communicationdevice initiates a backoff timer, which represents a duration of timethat the device must sense the medium to be idle before it is permittedto transmit. The backoff timer is decremented by one slot each time themedium is sensed to be idle during a corresponding slot interval. If thechannel remains idle until the backoff timer expires, the wirelesscommunication device becomes the holder (or “owner”) of a transmitopportunity (TXOP) and may begin transmitting. The TXOP is the durationof time the wireless communication device can transmit frames over thechannel after it has won contention for the wireless medium. If, on theother hand, one or more of the carrier sense mechanisms indicate thatthe channel is busy, a MAC controller within the wireless communicationdevice will not permit transmission.

Some APs and STAs may be configured to implement spatial reusetechniques. For example, APs and STAs configured for communicationsusing IEEE 802.11ax or 802.11be may be configured with a BSS color. APsassociated with different BSSs may be associated with different BSScolors. If an AP or a STA detects a wireless packet from anotherwireless communication device while contending for access, the AP or STAmay apply different contention parameters based on whether the wirelesspacket is transmitted by, or transmitted to, another wirelesscommunication device within its BSS or from a wireless communicationdevice from an overlapping BSS (OBSS), as determined by a BSS colorindication in a preamble of the wireless packet. For example, if the BSScolor associated with the wireless packet is the same as the BSS colorof the AP or STA, the AP or STA may use a first received signal strengthindication (RSSI) detection threshold when performing a CCA on thewireless channel. However, if the BSS color associated with the wirelesspacket is different than the BSS color of the AP or STA, the AP or STAmay use a second RSSI detection threshold in lieu of using the firstRSSI detection threshold when performing the CCA on the wirelesschannel, the second RSSI detection threshold being greater than thefirst RSSI detection threshold. In this way, the requirements forwinning contention are relaxed when interfering transmissions areassociated with an OBSS.

FIG. 4 shows a block diagram of an example wireless communication device400. In some implementations, the wireless communication device 400 canbe an example of a device for use in a STA such as one of the STAs 104described above with reference to FIG. 1. In some implementations, thewireless communication device 400 can be an example of a device for usein an AP such as the AP 102 described above with reference to FIG. 1.The wireless communication device 400 is capable of transmitting andreceiving wireless communications in the form of, for example, wirelesspackets. For example, the wireless communication device can beconfigured to transmit and receive packets in the form of physical layerconvergence protocol (PLCP) protocol data units (PPDUs) and mediumaccess control (MAC) protocol data units (MPDUs) conforming to an IEEE802.11 wireless communication protocol standard, such as that defined bythe IEEE 802.11-2016 specification or amendments thereof including, butnot limited to, 802.11ay, 802.11ax, 802.11az, 802.11ba and 802.11be.

The wireless communication device 400 can be, or can include, a chip,system on chip (SoC), chipset, package or device that includes one ormore modems 402, for example, a Wi-Fi (IEEE 802.11 compliant) modem. Insome implementations, the one or more modems 402 (collectively “themodem 402”) additionally include a WWAN modem (for example, a 3GPP 4GLTE or 5G compliant modem). In some implementations, the wirelesscommunication device 400 also includes one or more processors,processing blocks or processing elements 404 (collectively “theprocessor 404”) coupled with the modem 402. In some implementations, thewireless communication device 400 additionally includes one or moreradios 406 (collectively “the radio 406”) coupled with the modem 402. Insome implementations, the wireless communication device 400 furtherincludes one or more memory blocks or elements 408 (collectively “thememory 408”) coupled with the processor 404 or the modem 402.

The modem 402 can include an intelligent hardware block or device suchas, for example, an application-specific integrated circuit (ASIC),among other examples. The modem 402 is generally configured to implementa PHY layer, and in some implementations, also a portion of a MAC layer(for example, a hardware portion of the MAC layer). For example, themodem 402 is configured to modulate packets and to output the modulatedpackets to the radio 406 for transmission over the wireless medium. Themodem 402 is similarly configured to obtain modulated packets receivedby the radio 406 and to demodulate the packets to provide demodulatedpackets. In addition to a modulator and a demodulator, the modem 402 mayfurther include digital signal processing (DSP) circuitry, automaticgain control (AGC) circuitry, a coder, a decoder, a multiplexer and ademultiplexer. For example, while in a transmission mode, data obtainedfrom the processor 404 may be provided to an encoder, which encodes thedata to provide coded bits. The coded bits may then be mapped to anumber N_(SS) of spatial streams for spatial multiplexing or a numberN_(STS) of space-time streams for space-time block coding (STBC). Thecoded bits in the streams may then be mapped to points in a modulationconstellation (using a selected MCS) to provide modulated symbols. Themodulated symbols in the respective spatial or space-time streams may bemultiplexed, transformed via an inverse fast Fourier transform (IFFT)block, and subsequently provided to the DSP circuitry (for example, forTx windowing and filtering). The digital signals may then be provided toa digital-to-analog converter (DAC). The resultant analog signals maythen be provided to a frequency upconverter, and ultimately, the radio406. In implementations involving beamforming, the modulated symbols inthe respective spatial streams are precoded via a steering matrix priorto their provision to the IFFT block.

While in a reception mode, the DSP circuitry is configured to acquire asignal including modulated symbols received from the radio 406, forexample, by detecting the presence of the signal and estimating theinitial timing and frequency offsets. The DSP circuitry is furtherconfigured to digitally condition the signal, for example, using channel(narrowband) filtering and analog impairment conditioning (such ascorrecting for I/Q imbalance), and by applying digital gain toultimately obtain a narrowband signal. The output of the DSP circuitrymay then be fed to the AGC, which is configured to use informationextracted from the digital signals, for example, in one or more receivedtraining fields, to determine an appropriate gain. The output of the DSPcircuitry also is coupled with a demultiplexer that demultiplexes themodulated symbols when multiple spatial streams or space-time streamsare received. The demultiplexed symbols may be provided to ademodulator, which is configured to extract the symbols from the signaland, for example, compute the logarithm likelihood ratios (LLRs) foreach bit position of each subcarrier in each spatial stream. Thedemodulator is coupled with the decoder, which may be configured toprocess the LLRs to provide decoded bits. The decoded bits may then bedescrambled and provided to the MAC layer (the processor 404) forprocessing, evaluation or interpretation.

The radio 406 generally includes at least one radio frequency (RF)transmitter (or “transmitter chain”) and at least one RF receiver (or“receiver chain”), which may be combined into one or more transceivers.For example, each of the RF transmitters and receivers may includevarious analog circuitry including at least one power amplifier (PA) andat least one low-noise amplifier (LNA), respectively. The RFtransmitters and receivers may, in turn, be coupled to one or moreantennas. For example, in some implementations, the wirelesscommunication device 400 can include, or be coupled with, multipletransmit antennas (each with a corresponding transmit chain) andmultiple receive antennas (each with a corresponding receive chain). Thesymbols output from the modem 402 are provided to the radio 406, whichthen transmits the symbols via the coupled antennas. Similarly, symbolsreceived via the antennas are obtained by the radio 406, which thenprovides the symbols to the modem 402.

The processor 404 can include an intelligent hardware block or devicesuch as, for example, a processing core, a processing block, a centralprocessing unit (CPU), a microprocessor, a microcontroller, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a programmable logic device (PLD) such as a field programmablegate array (FPGA), discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. The processor 404 processes information receivedthrough the radio 406 and the modem 402, and processes information to beoutput through the modem 402 and the radio 406 for transmission throughthe wireless medium. For example, the processor 404 may implement acontrol plane and at least a portion of a MAC layer configured toperform various operations related to the generation, transmission,reception and processing of MPDUs, frames or packets. In someimplementations, the MAC layer is configured to generate MPDUs forprovision to the PHY layer for coding, and to receive decodedinformation bits from the PHY layer for processing as MPDUs. The MAClayer may further be configured to allocate time and frequencyresources, for example, for OFDMA, among other operations or techniques.In some implementations, the processor 404 may generally control themodem 402 to cause the modem to perform various operations describedabove.

The memory 408 can include tangible storage media such as random-accessmemory (RAM) or read-only memory (ROM), or combinations thereof. Thememory 408 also can store non-transitory processor- orcomputer-executable software (SW) code containing instructions that,when executed by the processor 404, cause the processor to performvarious operations described herein for wireless communication,including the generation, transmission, reception and interpretation ofMPDUs, frames or packets. For example, various functions of componentsdisclosed herein, or various blocks or steps of a method, operation,process or algorithm disclosed herein, can be implemented as one or moremodules of one or more computer programs.

FIG. 5A shows a block diagram of an example AP 502. For example, the AP502 can be an example implementation of the AP 102 described withreference to FIG. 1. The AP 502 includes a wireless communication device(WCD) 510 (although the AP 502 may itself also be referred to generallyas a wireless communication device as used herein). For example, thewireless communication device 510 may be an example implementation ofthe wireless communication device 4000 described with reference to FIG.4. The AP 502 also includes multiple antennas 520 coupled with thewireless communication device 510 to transmit and receive wirelesscommunications. In some implementations, the AP 502 additionallyincludes an application processor 530 coupled with the wirelesscommunication device 510, and a memory 540 coupled with the applicationprocessor 530. The AP 502 further includes at least one external networkinterface 550 that enables the AP 502 to communicate with a core networkor backhaul network to gain access to external networks including theInternet. For example, the external network interface 550 may includeone or both of a wired (for example, Ethernet) network interface and awireless network interface (such as a WWAN interface). Ones of theaforementioned components can communicate with other ones of thecomponents directly or indirectly, over at least one bus. The AP 502further includes a housing that encompasses the wireless communicationdevice 510, the application processor 530, the memory 540, and at leastportions of the antennas 520 and external network interface 550.

FIG. 5B shows a block diagram of an example STA 504. For example, theSTA 504 can be an example implementation of the STA 104 described withreference to FIG. 1. The STA 504 includes a wireless communicationdevice 515 (although the STA 504 may itself also be referred togenerally as a wireless communication device as used herein). Forexample, the wireless communication device 515 may be an exampleimplementation of the wireless communication device 400 described withreference to FIG. 4. The STA 504 also includes one or more antennas 525coupled with the wireless communication device 515 to transmit andreceive wireless communications. The STA 504 additionally includes anapplication processor 535 coupled with the wireless communication device515, and a memory 545 coupled with the application processor 535. Insome implementations, the STA 504 further includes a user interface (UI)555 (such as a touchscreen or keypad) and a display 565, which may beintegrated with the UI 555 to form a touchscreen display. In someimplementations, the STA 504 may further include one or more sensors 575such as, for example, one or more inertial sensors, accelerometers,temperature sensors, pressure sensors, or altitude sensors. Ones of theaforementioned components can communicate with other ones of thecomponents directly or indirectly, over at least one bus. The STA 504further includes a housing that encompasses the wireless communicationdevice 515, the application processor 535, the memory 545, and at leastportions of the antennas 525, UI 555, and display 565.

Various implementations relate generally to coordinated transmit powercontrol for sharing time and frequency resources of a wireless medium.Particular implementations relate more specifically to coordinated AP(CAP) spatial-reuse-multiple-access (SRMA) techniques for sharing thetime and frequency resources of a TXOP. According to such techniques, anAP that wins contention and gains access to the wireless medium for theduration of a TXOP (referred to as the TXOP owner) may limit thetransmit powers of the APs selected to share the time and frequencyresources such that interference from the selected APs does not preventSTAs associated with the TXOP owner from successfully decoding packetstransmitted by the TXOP owner.

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. In some implementations, the described techniquescan be used to reduce latency because the TXOP owner may share a TXOPwith other APs, and as such, the other APs may not need to wait to wincontention for a TXOP to be able to transmit and receive data accordingto conventional CSMA/CA or EDCA techniques. Additionally oralternatively, some implementations can achieve improvements inthroughput fairness. Various implementations may achieve these and otheradvantages without requiring that the TXOP owner or the other APsselected to participate in the TXOP be aware of the STAs associated withother BSSs (OBSSs), without requiring a preassigned or dedicated masterAP or preassigned groups of APs, and without requiring backhaulcoordination between the APs participating in the TXOP.

FIG. 6 shows a flowchart illustrating an example process 600 forcoordinated wireless communication that supports resource sharingaccording to some implementations. The operations of the process 600 maybe implemented by an AP or its components as described herein. Forexample, the process 600 may be performed by a wireless communicationdevice such as the wireless communication device 400 described abovewith reference to FIG. 4. In some implementations, the process 600 maybe performed by an AP, such as one of the APs 102 and 502 describedabove with reference to FIGS. 1 and 5A, respectively.

In some implementations, in block 602, the wireless communication device(hereinafter referred to as the first AP or TXOP owner) obtains a TXOPfor wireless communication via a wireless channel. In block 604, theTXOP owner selects one or more other coordinated wireless APs toparticipate in the TXOP. In block 606, the first AP determines a maximumtransmit power permitted to be used by each of the one or more selectedAPs or its respective stations for transmissions during the transmissionopportunity. In block 608, the first AP transmits a message to the oneor more selected access points that includes, for each of the selectedAPs an indication of time and frequency resources of the transmissionopportunity usable by the access point to transmit data to, or receivedata from, one or more respective wireless stations associated with theaccess point during the transmission opportunity. The message furtherincludes, for each of the selected APs, an indication of the maximumtransmit power for the access point. In block 610, the first APtransmits data to, or receives data from, one or more first wirelessSTAs associated with the first AP using the indicated time and frequencyresources.

FIG. 7 shows a timing diagram illustrating the transmissions ofcommunications in the example process of FIG. 6. In the exampleillustrated in FIG. 7, the TXOP owner (AP1) obtains a TXOP 702 andshares it with multiple other APs (AP2, AP3 and AP4). As illustrated inFIG. 7, in some implementations of the process 600, the TXOP 702includes multiple phase or stages including a first TXOP indicationphase 704, a second schedule allocation phase 706, and a third datatransmission phase 708.

In some implementations, to obtain the TXOP 702 in block 602, the firstAP contends for access to the wireless medium on one or more channelsincluding a primary operating channel (for example, a primary 20 MHzchannel and one or more secondary 20 MHz, 40 MHz, 80 MHz or 160 MHzchannels) using, for example, CSMA/CA and enhanced distributed channelaccess (EDCA) techniques. The TXOP 702 may be obtained at time to for awideband wireless channel, such as a bonded channel formed by theprimary channel and the one or more secondary channels. For example, thewideband wireless channel may be a 40 MHz, 80 MHz, 160 MHz or 320 MHzchannel.

In some implementations, to select the one or more other APs toparticipate in the TXOP in block 604, the TXOP owner AP1 performs a TXOPavailability indication process during the TXOP indication phase 704during which the TXOP owner AP1 learns of the other APs' desires orintents to participate in the TXOP 702. For example, FIG. 8 shows aflowchart illustrating an example TXOP indication process 800 foradvertising an availability of time and frequency resources in the TXOP702. In some implementations, after obtaining the TXOP 702 in block 602of the process 600, the TXOP owner AP1 transmits, in block 802 of theprocess 800, a first frame 710 to at least one station (STA1) associatedwith the TXOP owner AP1 at time t₁. For example, the first frame 710 maybe a control frame. In some implementations, the first frame 710 is arequest-to-send (RTS) frame (hereinafter the first frame 710 will bereferred to as the RTS frame 710, although other possibilities exist)addressed to the STA1. In some other implementations, the RTS frame 710may be an MU-RTS frame intended for multiple STAs associated with theTXOP owner AP1. The RTS frame 710 is configured to cause the STA1 totransmit a clear-to-send (CTS) frame 712 at time t₂. Any other wirelesscommunication devices, including the APs AP2, AP3 and AP4, and theirassociated STAs, that receive either or both of the RTS frame 710 or theCTS frame 712 may set their respective network allocation vectors (NAVs)for a duration of time indicated in the RTS or CTS frames.

In block 804, the TXOP owner AP1 receives the CTS frame 712 from theSTA1 and, in block 806, measures or otherwise determines a receivedpower (RX power) of the CTS frame 712. In some implementations, theother APs, including AP2, AP3 and AP4, are further configured to measurethe RX power of the CTS frame 712. For example, the TXOP owner AP1 andthe other APs may be configured to determine a received signal strengthindication (RSSI) value for the CTS frame 712.

In block 808, at time t₃, the TXOP owner AP1 transmits a third frame(also referred to herein as a CAP TXOP indication (CTI) frame) 714 toother wireless APs, for example, other APs in its extended service set(ESS), that indicates that the time and frequency resources of the TXOP702 can be shared by the TXOP owner AP1. For example, the TXOP owner AP1may have previously become aware of the other neighboring APs in itsvicinity based on information in beacons or other management framesreceived from the other APs.

In block 810, after transmitting the CTI frame 714, the TXOP owner AP1may receive, at time t₄, a fourth frame (also referred to herein as aCAP TXOP request (CTR) frame) 716 from each of one or more candidate APsthat indicates a desire by the respective AP to participate in the TXOP702. In the example illustrated in FIG. 7, AP2, AP3 and AP4 are amongthe candidate APs that transmit respective CTR frames 7162, 7163 and7164 to the TXOP owner AP1 in block 810. In some implementations, eachCTR frame 716 includes a power indication. For example, the powerindication may be the RX power of the CTS frame 712 measured by therespective AP. In some other implementations, the power indication maybe another metric, parameter or value based on the RX power. In someimplementations, the receipt of the CTR frame 716 or the powerindication may serve as the indication that the respective AP desires toparticipate in the TXOP 702.

In some implementations, the CTI frame 714 includes at least one triggerframe configured to trigger the one or more candidate APs to transmitthe respective CTR frames 716. To transmit the CTI frame 714, the TXOPowner AP1 may transmit a PPDU that includes a same CTI trigger frame ineach of multiple subchannels of the wireless channel (for example, ineach of multiple 20 MHz channels). For example, the CTI frame 714 mayinclude a non-high-throughput (non-HT) duplicate trigger frame in each20 MHz channel. In this way, the other APs do not need to be operatingon the same primary 20 MHz channel to receive and process the CTI frame714. In some implementations, a source address field and a BSSID field(for example, in a MAC header) associated with the CTI frame 714 may beset to the MAC address of the TXOP owner AP1 and a destination addressfield (for example, in the MAC header) associated with the CTI frame 714is set to a broadcast address.

Each duplicate trigger frame of the CTI frame 714 may include, for eachof the multiple APs that may participate in the TXOP, an indication ofone or both of frequency resources or spatial resources usable by therespective AP to transmit its respective CTR frame 716. For example,each trigger frame of the CTI frame 714 may include a user informationfield for each of the access points that includes the respectiveindication of the frequency resources or the spatial resources the AP isto use to transmit its CTR frame 716. Each user information field mayinclude a respective AP identifier (APID) of the respective AP. Forexample, the APID may be a MAC address of the AP, a BSSID associatedwith the AP or a BSS color associated with the AP. In some otherimplementations in which the TXOP owner AP1 may not be aware of some orall of the neighboring APs, the CTI frame 714 may include an indicationof random access resources usable by the APs to transmit theirrespective CTR frames 712.

The CTR frames 716 may be received from the candidate APs in respectivetrigger-based PPDUs in response to the CTI frame 714 using the frequencyor spatial resources allocated by the CTI frame 714. For example, theCTR frames 716 may be transmitted via MU OFDMA or MU MIMO techniques andmay be received at time t₄ a SIFS duration after the CTI frame 714. Forthe APs capable of CAP SRMA, the CTI frame 714 may be configured tocause the APs to respond with respective CTR frames 716 regardless oftheir respective NAVs.

In some implementations, the TXOP owner AP1 may transmit multiple CTIframes 714, each to a respective one of the APs, on an AP-by-APsequential basis. An AP desiring to participate in the TXOP maytransmit, in response to receiving a respective one of the CTI frames714, a CTR frame 716 before the transmission of a next CTI frame 714 toa next one of the APs. For example, each CTI frame 714 may be a pollframe and each CTR frame 716 may be a poll response frame. Such CTIframes 714 and CTR frames 716 may be transmitted as single-user (SU)transmissions. In some other implementations, the TXOP owner AP1 maytransmit a single CTI frame 714, and subsequently, transmit a pollingframe (poll) to each of the APs, on an AP-by-AP sequential basis, thatsolicits a response CTR frame 716 from the respective AP before thetransmission of a poll to a next one of the APs.

Referring back to the process 600, based on the receipt of the CTRframes 716, the TXOP owner AP1 may then select one or more of thecandidate APs to participate in the TXOP 702 in block 604. The TXOPowner AP1 selects the APs to participate in the TXOP 702 from thecandidate APs based on the power indications received in the CTR frames716. The TXOP owner AP1 may select the APs such that it still protectsits own transmissions (which may be referred to as primarytransmissions) to and from the STAs in its BSS. Prior to selecting theAPs to participate, the TXOP owner AP1 may already be aware of theacceptable signal-to-interference ratios (SIRs) at its associated STAsthat enable the successful decoding of the packets for each of one ormore selectable MCSs.

The acceptable SIR (or SIR threshold) at a given STA may be quantifiedas Equation 1 below, where TX_(AP1) is the TX power the TXOP owner AP1intends to transmit at, TX_(CAP) is the TX power of a respective one ofthe candidate APs (including AP2, AP3 and AP4), PL_(AP1) is the pathlossbetween the TXOP owner AP1 and the associated STA that transmitted theCTS frame 712 (STA1), and PL_(CAP) is the pathloss between therespective one of the candidate APs and STA1.SIR=(TX _(AP1) −PL _(AP1))−(TX _(CAP) −PL _(CAP))  (1)The pathlosses PL_(AP1) and PL_(CAP) can, in turn, be represented asEquations 2 and 3 below.PL _(AP1) =TX _(STA) −RX _(AP1-STA)  (2)PL _(CAP) =TX _(STA) −RX _(CAP-STA)  (3)where TX_(STA) is the TX power of STA1 and RX_(AP1-STA) is the RX powerof the CTS frame 712 at the TXOP owner AP1. The TXOP owner AP1 mayselect AP2, AP3 and AP4 from the candidate APs to participate in theTXOP 702 based on the pathlosses in block 604.

Referring again back to the process 600, the TXOP owner AP1 may, inblock 606, calculate or otherwise determine the TX power TX_(AP1) thatit will transmit at for transmissions to one or more associated STAsincluding STA1 during the data transmission phase 708. Similarly, theTXOP owner AP1 may calculate or otherwise determine a respective maximumtransmit power TX_(MAX) for each of the selected APs AP2, AP3 and AP4based on the acceptable SIR and the power indications received from theselected APs. For example, based on rearranging Equation 1 above, themaximum TX power TX_(MAX) for each one of the selected APs may beexpressed as Equation 4 below, where the SIR term represents athreshold, which may be different than the acceptable SIR.TX _(MAX) =TX _(AP1) +PL _(CAP) −PL _(AP1) −SIR  (4)Based on substituting Equations 2 and 3 into Equation 4, the maximum TXpower TX_(MAX) for a given one of the selected APs may be re-expressedas Equation 5 below.TX _(MAX) =TX _(AP1) +RX _(AP1-STA) −RX _(CAP-STA) −SIR  (5)

As such, the TXOP owner AP1 can determine the maximum TX power TX_(MAX)for each one of the selected APs using Equation 5 based on theacceptable SIR for STA1, its own TX power TX_(AP1), its measurement ofthe RX power RX_(AP1-STA) of the CTS frame 712, and the RX powerRX_(CAP-STA) of the CTS frame 712 indicated in the CTR frame 716 fromthe respective AP.

After selecting the APs to participate in the TXOP 702 during the TXOPindication phase 704, the TXOP owner AP1 then grants, schedules orotherwise actually allocates (for example, indicates the allocations of)the respective time and frequency resources and maximum TX powers to theselected APs in the schedule allocation phase 706. For example, FIG. 9shows a flowchart illustrated an example schedule allocation process 900for allocating time and frequency resources in the TXOP 702. In block902, at time t₅, the TXOP owner AP1 transmits a fifth frame (referred toherein as a CAP TXOP AP schedule (CTAS) frame) 718 that identifies theselected APs and that includes the indication of the time and frequencyresources available in the data transmission phase 708. In someimplementations, the CTAS frame 718 further includes, for each of theselected APs, an indication of the maximum TX power usable by therespective AP to transmit data to, or receive data from, one or morerespective associated STAs during the TXOP 702 via the time andfrequency resources. For example, block 902 of the process 900 may be anexample implementation of block 608 of the process 600. For example, theCTAS frame 718 may be transmitted at time is a SIFS duration after theCTR frames 716.

In block 904, after transmitting the CTAS frame 718, the TXOP owner AP1may transmit, at time t₆, a sixth frame (referred to herein as a CAPTXOP Local Schedule (CTLS) frame) 720 ₁ to one or more associated STAsin its BSS. Similarly, each of the selected APs AP2, AP3 and AP4 mayalso transmit respective CTLS frames 720 ₂, 720 ₃ and 720 ₄,respectively, to the associated wireless STAs in their respective BSSsat time t₆. Each of the CTLS frames 720 identifies the time andfrequency resources as well as the maximum TX power allocated to therespective AP and its associated BSS. For the APs capable of CAP SRMA,the CTAS frame 718 may be configured to cause the selected APs totransmit the respective CTLS frames 720 regardless of their respectiveNAVs.

In some implementations, the CTAS frame 718 includes at least onetrigger frame configured to trigger the selected APs AP2, AP3 and AP4 totransmit the respective CTLS frames 720 ₂, 720 ₃ and 720 ₄ to theirassociated BSSs simultaneously with the TXOP owner AP1 transmitting theCTLS frame 720 ₁ to its associated BSS at time t₆, for example, a SIFSduration after the CTAS frame 718. To transmit the CTAS frame 718, theTXOP owner AP1 may transmit a PPDU that includes a same CTAS triggerframe in each of multiple subchannels of the wireless channel (forexample, in each of multiple 20 MHz channels). For example, the CTASframe 718 may include a non-HT duplicate trigger frame in each 20 MHzchannel. In this way, the other APs do not need to be operating on thesame primary 20 MHz channel to receive and process the CTAS frame 718.In some implementations, a source address field and a BSSID field (forexample, in a MAC header) associated with the CTAS frame 718 may be setto the MAC address of the TXOP owner AP1 and a destination address field(for example, in the MAC header) associated with the CTAS frame 718 maybe set to a broadcast address.

Each duplicate trigger frame of the CTAS frame 718 may include anindication of the time and frequency resources available for use duringthe data transmission phase 708. For example, each trigger frame of theCTAS frame 718 may include a user information field for each of theselected APs. Each user information field may include or be identifiedby a respective APID of the respective AP. For example, the APID may bea MAC address of the AP, a BSSID associated with the AP or a BSS colorassociated with the AP. Each user information field may include, for therespective AP, an indication of the available time and frequencyresources (or a particular allocation of the time and frequencyresources allocated to the respective AP) for use during the datatransmission phase 708. For example, each user information field mayinclude an indication of a starting time of the available or allocatedtime resources, such as, an indication of a symbol, a slot or anabsolute or relative time at which the time resources begin. The userinformation field may also include a duration of the respective timeresources, for example, in units of symbols, slots or milliseconds (ms).Each user information field may additionally include an indication offrequency resources available for use by or allocated to the respectiveAP. For example, the user information field may indicate one or morechannels or subchannels (for example, one or more 20 MHz channels) orone or more resource units (RUs) usable by the respective AP.

Each duplicate trigger frame of the CTAS frame 718 may further include,for each of the selected APs, an indication of the maximum TX powerpermitted to be used by the respective AP during the data transmissionphase 708. For example, in some implementations, each user informationfield includes a value (for example, in dBs per 20 MHz or in some otherunit) that explicitly indicates the respective maximum TX power for therespective AP, for example, as calculated based on Equation 5.Additionally or alternatively, in some implementations, the TXOP ownerAP1 may provide an implicit indication of the maximum TX power in theCTAS frame 718. For example, each user information field may include anindication of the maximum TX power in the form of, for example, anindication of the TX power TX_(AP1) of the TXOP owner AP1, an indicationof AP1's measurement of the RX power RX_(AP1-STA) of the CTS frame 712,and an indication of the SIR. In such examples, each selected APreceiving the CTAS frame 718 may determine the value of its maximumpermitted TX power TX_(MAX) based on the indications of TX_(AP1),RX_(AP1-STA), and the SIR received in the CTAS frame 718, based on itsown measured RX power RX_(CAP-STA) of the CTS frame 712, and based onEquation 5.

In some implementations or instances, the TXOP owner AP1 and one or moreof the selected APs AP2, AP3 and AP4 may be configured for communicationvia CAP SRMA as well as CAP TDMA or CAP OFDMA simultaneously. In otherimplementations or instances, the CTAS frame 718 may allocate all of theavailable time resources or all of the available frequency resources ofthe data transmission phase 708 to each of the selected APs.

In some implementations, the CTLS frames 720 transmitted by the TXOPowner AP1 and the selected APs AP2, AP3 and AP4 are non-HT duplicateframes. That is, in some implementations, each of the CTLS frames 720 isidentical to the others. Additionally, each of the CTLS frames 720transmitted by the TXOP owner AP1 and the selected APs AP2, AP3 and AP4may be transmitted simultaneously via all of the available frequencyresources of the wireless channel. In this way, the CTLS frames 720 willnot destructively interfere with each other and the STAs receiving theCTLS frames 720 may properly decode them. In some implementations, asource address field (for example, in a MAC header) associated with eachof the CTLS frames 720 is set to the same multicast address or otherpredefined address associated with CAP SRMA transmissions. STAssupporting CAP SRMA may be configured such that when they receive frameshaving the multicast address, they decode and parse the respectiveframes. In some implementations, a BSSID field (for example, in the MACheader) associated with each of the CTLS frames 720 is set to the BSSIDof the TXOP owner AP1. In some such implementations, a destinationaddress field (for example, in the MAC header) associated with each ofthe CTLS frames 720 is set to the same broadcast address.

In some implementations, each of the CTLS frames 720 transmitted by theTXOP owner AP1 and the selected APs AP2, AP3 and AP4 includes aninformation element (IE) or other field for each of the APs AP1, AP2,AP3 and AP4 (and its associated BSS) that includes, for the respectiveAP or BSS, an indication of the available time and frequency resources(or a particular allocation of the time and frequency resourcesallocated to the respective AP or BSS). For example, each IE may includean indication of the starting time of the available or allocated timeresources, such as, an indication of a symbol, a slot or an absolute orrelative time at which the time resources begin. The IE may also includean indication of the duration of the time resources, for example, inunits of symbols, slots or ms. Each IE may additionally include anindication of the frequency resources available for use by or allocatedto the respective AP or BSS. For example, the IE may indicate one ormore channels or subchannels (for example, one or more 20 MHz channels)or one or more RUs usable by the respective AP and its BSS. Each IE mayfurther include an indication of the maximum TX power permitted to beused by the respective AP and the STAs within its BSS during the datatransmission phase 708. Because the STAs associated with the selectedAPs may not be in range of, or otherwise be able to receive and processthe CTAS frame 718, the use of the CTLS frames 720 ensures that the STAsbecome aware of the time and frequency resources, as well as the maximumpermitted TX power, and informs the STAs that they should be in anactive listening mode to monitor for the identified time and frequencyresources.

After the AP and local scheduling during the schedule allocation phase706, the data transmission phase 708 may begin. As described above, inblock 610, the TXOP owner AP1 and the selected APs AP2, AP3 and AP4 mayshare the time and frequency resources of the TXOP to perform or enabledownlink (DL) or uplink (UL) communications with their respectiveassociated STAs. In some implementations, the TXOP owner AP1 maysynchronize the coordinated APs in time. For example, in someimplementations, in a beginning portion of the data transmission phase708, the TXOP owner AP1 transmits a trigger frame (referred to herein asa CAP TXOP trigger (CTTRIG) frame) 722 to the selected access points attime t₇ (after the CTLS frames 720 are transmitted) to synchronize intime the selected APs with the TXOP owner AP1.

In some implementations, in addition to, or as an alternative to,indicating the maximum TX power for each of the selected APs in the CTASframe 718, the TXOP owner AP1 may indicate the maximum TX powers in theCTTRIG frame 722. For example, the CTTRIG frame 722 may include a userinformation field, IE or other field for each of the selected APs thatincludes a respective APID of the respective AP, such as a MAC addressof the AP, a BSSID associated with the AP or a BSS color associated withthe AP. Each user information field, IE or other field may also includean indication of the available time and frequency resources (or aparticular allocation of the time and frequency resources allocated tothe respective AP) as well as an indication of the maximum TX powerpermitted to be used by the respective AP and its BSS during the datatransmission phase 708.

In some implementations, data communications may begin a SIFS durationafter the CTTRIG frame 722. The APs capable of CAP SRMA may beconfigured to transmit and receive data communications, acknowledgement(ACK) frames, and trigger frames regardless of their respective NAVsduring the data transmission phase 708. Additionally, the STAscompatible with CAP SRMA may be configured to be in an active listeningmode during the data transmission phase 708 such that they may transmitand receive data communications, ACK frames, and trigger framesregardless of their respective NAVs.

For example, as illustrated in FIG. 7, the TXOP owner AP1 may transmitor receive one or more data communications 724 ₁ to or from one or moreSTAs in its BSS beginning at time is using some or all of the availabletime and frequency resources at or below a maximum TX power itdetermined for itself in the process 800. For example, the TXOP ownerAP1 may transmit a DL data communication (for example, a PPDU) 720 ₁including a data frame to multiple STAs using multi-user (MU) orthogonalfrequency division multiple access (OFDMA). Additionally oralternatively, the TXOP owner AP1 may transmit a data frame to multipleSTAs using MU multiple-input multiple-output (MIMO). Additionally oralternatively, the TXOP owner AP1 may transmit a data frame to a singleSTA using single-user (SU) techniques. In some such implementations inwhich the TXOP owner AP1 transmits one or more DL data communications724 ₁, the associated STAs may respond with ACK frames (such as BlockACKs (BAs)) also using some or all of the available time and frequencyresources of the data transmission phase 708.

In addition to, or as an alternative to, transmitting DL datacommunications, the TXOP owner AP1 may also receive one or more UL datacommunications 724 ₁ from one or more STAs in its BSS beginning at timeis using some or all of the available time and frequency resources. Eachof the STAs may transmit an UL data communication at a TX power equal toor less than the maximum TX power for its BSS. For example, the TXOPowner AP1 may transmit a trigger frame that triggers an UL datacommunication including multiple data frames from multiple STAs usingone or more of MU OFDMA or MU MIMO in the form of a MU PPDU, or an ULdata communication from each of one or more single STAs sequentially inthe form of respective SU PPDUs. In some such implementations in whichthe TXOP owner AP1 receives one or more UL data communications 724 ₁,the TXOP owner AP1 may respond with ACK frames (such as BAs) also usingsome or all of the available time and frequency resources of the datatransmission phase 708.

In some implementations, prior to transmitting any communications 724 ₁to any of its associated STAs, the TXOP owner AP1 may perform a CSMAoperation in a beginning portion of the data transmission phase 708. Forexample, the TXOP owner AP1 may perform physical carrier sensing, andspecifically energy detection, to determine whether the wireless mediumis idle prior to transmitting any data, trigger, management or controlframes during the data transmission phase 708. If the TXOP owner AP1senses that the wireless medium is not idle, it may forgo transmittingany communications in the data transmission phase 708. In someimplementations, one or more parameters for the carrier sensing may beindicated in the trigger frame 722.

Similar to the TXOP owner AP1, the second AP2 may transmit or receiveone or more data communications 7242 to or from one or more STAs in itsBSS beginning at time is using some of all of the available time andfrequency resources indicated by the TXOP owner during the scheduleallocation phase 706. Similarly, the third AP3 may transmit or receiveone or more data communications 7243 to or from one or more STAs in itsBSS beginning at time is using some of all of the available time andfrequency resources indicated by the TXOP owner during the scheduleallocation phase 706. Similarly, the fourth AP4 may transmit or receiveone or more data communications 7244 to or from one or more STAs in itsBSS beginning at time is using some of all of the available time andfrequency resources indicated by the TXOP owner during the scheduleallocation phase 706.

Also similar to the TXOP owner AP1, prior to transmitting anycommunications 724 to any of their associated STAs, the selected APs mayperform CSMA operations in a beginning portion of the data transmissionphase 708. For example, each of the selected APs may perform physicalcarrier sensing, and specifically energy detection, to determine whetherthe wireless medium is idle prior to transmitting any data, trigger,management or control frames, as described above with reference to theTXOP owner AP1.

In some implementations, the TXOP owner AP1 may partition the TXOP intomultiple schedule allocation phases 706 and multiple respective datatransmission phases 708 (each including time and frequency resourcesshared by multiple APs). In some such implementations, there may be onlyone TXOP indication phase 704 because the TXOP owner AP1 may only needto learn of each of the other APs' measured RX power of the CTS frameand intent to participate in the TXOP once.

FIG. 10 shows a flowchart illustrating an example process 1000 forcoordinated wireless communication that supports resource sharingaccording to some implementations. The operations of the process 1000may be implemented by an AP or its components as described herein. Forexample, the process 1000 may be performed by a wireless communicationdevice such as the wireless communication device 400 described abovewith reference to FIG. 4. In some implementations, the process 1000 maybe performed by an AP, such as one of the APs 102 and 502 describedabove with reference to FIGS. 1 and 5A, respectively.

In some implementations, in block 1002, the wireless communicationdevice (hereinafter referred to as AP2 from the selected APs in FIG. 7)receives a first frame from at least one STA associated with a second AP(for example, the TXOP owner AP1). In block 1004, AP2 measures orotherwise determines an RX power of the first frame. In block 1006, thefirst AP transmits a second frame to the TXOP owner AP1 that includes apower indication based on the received power. In block 1008, AP2 mayreceive a third frame from the TXOP owner AP1 that includes anindication of time and frequency resources of the TXOP usable by AP2 totransmit data to, or receive data from, one or more STAs associated withAP2 during the TXOP. The third frame further includes an indication of amaximum TX power permitted to be used by AP2 or its respectiveassociated STAs when transmitting using the time and frequencyresources. In block 1010, AP2 may then transmit data to, or receive datafrom, one or more of the STAs associated with AP2 using the indicatedtime and frequency resources at a power at or below the indicatedmaximum TX power.

In some examples, the first frame received in block 1002 is a controlframe, such as a CTS frame 712 transmitted in response to an RTS frame710 from the TXOP owner AP1. In some such examples, the RX powerdetermined in block 1004 may be an RSSI value for the CTS frame 712.

In some implementations, AP2 may, after receiving the first frame andprior to transmitting the second frame, receive a fourth frame from theTXOP owner AP1 that indicates that a plurality of time and frequencyresources of the TXOP 702 can be shared by the TXOP owner AP1. Forexample, the fourth frame may be a CTI frame 714, and the second frametransmitted by AP2 in block 1006 may be a CTR frame 716. In someimplementations, the CTI frame 714 includes at least one trigger frameconfigured to trigger AP2 to transmit the CTR frame 716. As describedabove, a source address field and a BSSID field (for example, in a MACheader) associated with the CTI frame 714 may be set to the MAC addressof the TXOP owner and a destination address field (for example, in theMAC header) associated with the CTI frame 714 may be set to a broadcastaddress.

As described above, the CTI frame 714 may include an indication of oneor both of frequency resources or spatial resources usable by AP2 totransmit its respective CTR frame 716. For example, each trigger frameof the CTI frame 714 may include a user information field for each ofthe APs participating in the TXOP 702, including AP2, that includes therespective indication of the frequency resources or the spatialresources AP2 is to use to transmit its CTR frame 716. As describedabove, the user information field for AP2 may include a respective APIDof AP2. For example, the APID may be a MAC address of AP2, a BSSIDassociated with AP2 or a BSS color associated with AP2. In some otherimplementations in which the TXOP owner AP1 may not be aware of some orall of the neighboring APs, the CTI frame 714 may include an indicationof random access resources usable by AP2 to transmit its respective CTRframe 716.

As described above, the CTR frame 716 may indicate a desire by AP2 toparticipate in the TXOP 702. In some implementations, as describedabove, the CTR frame 716 includes the power indication. For example, thepower indication may be the RX power of the CTS frame 712 measured byAP2. In some other implementations, the power indication may be anothermetric, parameter or value based on the RX power. In someimplementations, the transmission of the CTR frame 716 or the powerindication may serve as the indication that AP2 desires to participatein the TXOP 702.

AP2 may transmit the CTR frame 716 in a trigger-based PPDU in responseto the CTI frame 714 using the frequency or spatial resources allocatedby the CTI frame 714. For example, AP2 may transmit the CTR frame 716via MU OFDMA or MU MIMO techniques a SIFS duration after the CTI frame714. The CTI frame 714 may be configured to cause AP2 to respond withits CTR frame 716 regardless of its respective NAV. In some otherimplementations, the TXOP owner AP1 may transmit multiple CTI frames710, each to a respective one of the APs, on an access point-by-accesspoint sequential basis. For example, the CTI frame 714 may be a pollframe and the CTR frame 716 may be a poll response frame.

As described above, after transmitting the CTR frame 716, AP2 receives athird frame, for example, a CTAS frame 718 that identifies the APs,including AP2, selected to participate in the TXOP 702. The CTAS frame718 includes the indication of the available time and frequencyresources and the indication of the maximum transmit power usable by AP2to transmit data to, or receive data from, one or more respectiveassociated STAs during the data transmission phase 708. In someimplementations, a source address field and a BSSID field (for example,in a MAC header) associated with the CTAS frame 718 may be set to theMAC address of the TXOP owner AP1 and a destination address field (forexample, in the MAC header) associated with the CTAS frame 718 may beset to a broadcast address.

The CTAS frame 718 may include a user information field for each of aplurality of APs including AP2. The user information field for AP2 mayinclude an APID of AP2, such as a MAC address of AP2, a BSSID associatedwith AP2 or a BSS color associated with AP2. The user information fieldmay include an indication of a starting time and a duration of the timeresources available to AP2. For example, the user information field mayinclude an indication of a symbol, a slot or an absolute or relativetime at which the allocated time resources begin and a duration of therespective allocated time resources, for example, in units of symbols,slots or ms. The user information field may additionally include anindication of frequency resources (such as one or more channels,subchannels or RUs) available for use by AP2.

In some implementations, the user information field for AP2 furtherincludes the indication of the maximum TX power usable by AP2 totransmit data to, or receive data from, one or more respectiveassociated STAs during the data transmission phase 708 via the indicatedtime and frequency resources. For example, in some implementations, eachuser information field includes a value (for example, in dBs per 20 MHzor in some other unit) that explicitly indicates the maximum TX powerfor the respective AP, for example, as calculated based on Equation 5.Additionally or alternatively, in some implementations, the TXOP ownerAP1 may provide an implicit indication of the maximum TX power in theCTAS frame 718. For example, each user information field may include anindication of the maximum TX power in the form of, for example, anindication of the TX power TX_(AP1) of the TXOP owner AP1, an indicationof AP1's measurement of the RX power RX_(AP1-SPA) of the CTS frame 712,and an indication of the SIR. In such examples, AP2 may calculate orotherwise determine the maximum transmit power TX_(MAX) it is permittedto use based on the indications of TX_(AP1), RX_(AP1-STA), and the SIRreceived in the CTAS frame 718, based on its own measured RX powerRX_(CAP-STA) of the CTS frame 712, and based on Equation 5.

In some implementations, the process 1000 may further includetransmitting an additional frame, for example, a CTLS frame 720, to oneor more of its associated STAs in its BSS that identifies the availabletime and frequency resources and that indicates the maximum TX power. Asdescribed above, the CTAS frame 718 may include a trigger frame thattriggers AP2 to transmit the CTLS frame 720 to its associated BSSsimultaneously with the TXOP owner AP1 transmitting a CTLS frame 720 toits associated BSS. The CTAS frame 718 may be configured to cause AP2 totransmit the CTLS frame 720 regardless of its NAV.

As described above, the CTLS frame 720 may be a non-HT duplicate framethat, in some implementations, may be transmitted simultaneously via allof the available frequency resources of the wireless channel. In someimplementations, a source address field (for example, in a MAC header)associated with the CTLS frame 720 is set to a multicast address orother predefined address associated with CAP SRMA transmissions. In somesuch implementations, a BSSID field (for example, in the MAC header)associated with each of the CTLS frames 720 is set to the BSSID of theTXOP owner. In some such implementations, a destination address field(for example, in the MAC header) associated with the CTLS frame 720 isset to a broadcast address.

As described above, in some implementations, the CTLS frame 720transmitted by AP2 includes an IE or other field that includes anindication of the available time and frequency resources (or aparticular allocation of the time and frequency resources allocated toAP2 and its BSS). For example, the IE may include an indication of thestarting time of the available or allocated time resources, such as, anindication of a symbol, a slot or an absolute or relative time at whichthe time resources begin. The IE may also include an indication of theduration of the time resources, for example, in units of symbols, slotsor ms. Each IE may additionally include an indication of the frequencyresources available for use by or allocated to AP2 and its BSS. Forexample, the IE may indicate one or more channels or subchannels (forexample, one or more 20 MHz channels) or one or more RUs usable by AP2and its BSS. The IE may further include an indication of the maximum TXpower permitted to be used by AP2 and its BSS during the datatransmission phase 708.

After transmitting the CTLS frame 720, AP2 may receive a CTTRIG frame722 that synchronizes in time AP2 with the TXOP owner AP1. In someimplementations, data communications may begin a SIFS duration after theCTTRIG frame 722. As described above, in some implementations, inaddition to, or as an alternative to, indicating the maximum TX powerfor each of the selected APs in the CTAS frame 718, the TXOP owner AP1may indicate the maximum TX powers in the CTTRIG frame 722. For example,the CTTRIG frame 722 may include a user information field, IE or otherfield for AP2 that includes a respective APID of AP2, such as a MACaddress, a BSSID or a BSS color associated with AP2. The userinformation field, IE or other field may also include an indication ofthe available time and frequency resources (or a particular allocationof the time and frequency resources allocated to AP2) as well as anindication of the maximum TX power permitted to be used by AP2 and itsBSS during the data transmission phase 708.

AP2 may be configured to transmit and receive data communications, ACKframes, and trigger frames regardless of its NAV during the datatransmission phase 708. After receiving the CTTRIG frame 722, AP2 maytransmit or receive one or more data communications 724 to or from oneor more STAs in its BSS using the allocated time and frequencyresources. For example, AP2 may transmit a DL data communication (forexample, a PPDU) 724 including a data frame to multiple STAs using oneor both of MU OFDMA or MU MIMO in the form of a MU PPDU, or may transmitone or more DL data communications to one STA at a time sequentiallyusing SU techniques in the form of a SU PPDU. In some suchimplementations in which AP2 transmits one or more DL datacommunications 724, the associated STAs may respond with ACK frames alsousing one or more of the time and frequency resources available to AP2and its BSS.

In addition to, or as an alternative to, transmitting DL datacommunications, AP2 may also receive one or more UL data communications724 from one or more STAs in its BSS using the available time andfrequency resources. For example, AP2 may transmit a trigger frame usingthe allocated resources that triggers an UL data communication includingmultiple data frames from multiple STAs using one or more of MU OFDMA orMU MIMO in the form of a MU PPDU, or an UL data communication from eachof one or more single STAs sequentially in the form of respective SUPPDUs. In some such implementations in which AP2 receives one or more ULdata communications 724, it may respond with ACK frames (such as BAs)also using one or more of the time and frequency resources available toAP2 and its BSS.

FIG. 11 shows a block diagram of an example wireless communicationdevice 1100 that supports resource sharing according to someimplementations. In some implementations, the wireless communicationdevice 1100 is configured to perform one or more of the processes 600and 1000 described above with reference to FIGS. 6 and 10, respectively.The wireless communication device 1100 may be an example implementationof the wireless communication device 400 described above with referenceto FIG. 4. For example, the wireless communication device 1100 can be achip, SoC, chipset, package or device that includes at least oneprocessor and at least one modem (for example, a Wi-Fi (IEEE 802.11)modem or a cellular modem). In some implementations, the wirelesscommunication device 1100 can be a device for use in an AP, such as oneof the APs 102 and 502 described above with reference to FIGS. 1 and 5A,respectively. In some other implementations, the wireless communicationdevice 1100 can be an AP that includes such a chip, SoC, chipset,package or device as well as at least one transmitter, at least onereceiver, and at least one antenna.

The wireless communication device 1100 includes a channel access module1102, a candidate selection module 1104, a power measurement module1106, a TX power determination module 1108, a resource allocation module1110, and a transmission and reception (TX/RX) module 1112. Portions ofone or more of the modules 1102, 1104, 1106, 1108, 1110 and 1112 may beimplemented at least in part in hardware or firmware. For example, thechannel access module 1102, the power measurement module 1106 and theTX/RX module 1112 may be implemented at least in part by a modem (suchas the modem 402). In some implementations, at least some of the modules1102, 1104, 1106, 1108, 1110 and 1112 are implemented at least in partas software stored in a memory (such as the memory 408). For example,portions of one or more of the modules 1102, 1104, 1106, 1108, 1110 and1112 can be implemented as non-transitory instructions (or “code”)executable by a processor (such as the processor 406) to perform thefunctions or operations of the respective module.

The channel access module 1102 is configured to obtain a TXOP forwireless communication via a wireless channel including multiple timeand frequency resources. For example, the channel access module 1102 maybe configured to perform block 602 of the process 600 described withreference to FIGS. 6-9. In some implementations, to obtain the TXOP, thechannel access module 1102 contends for access to the wireless medium onone or more channels including a primary operating channel (for example,a primary 20 MHz channel and one or more secondary 20 MHz, 40 MHz, 80MHz or 160 MHz channels) using, for example, CSMA/CA and enhanceddistributed channel access (EDCA) techniques.

The candidate selection module 1104 is configured to select one or moreother candidate wireless APs to participate in the TXOP. For example,the candidate selection module 1104 may be configured to perform block604 of the process 600 described with reference to FIGS. 6-9. Beforemaking the selection, the TX/RX module 1108 is configured to transmit anRTS frame to at least one of its associated STAs that elicits thetransmission of a CTS frame from at least one of the STAs. For example,the TX/RX module 1108 may be configured to perform blocks 802 and 804 ofthe process 800 described with reference to FIG. 8. As described above,the APs, including the wireless communication device 1100, receiving theCTS frame may then measure the RX power of the CTS frame. For example,the power measurement module 1106 may be configured to perform block 806of the process 800 to measure or otherwise determine an RX power or RSSIof the CTS frame.

So that the candidate selection module 1104 can make the selection, theTX/RX module 1108 is further configured to transmit a CTI frame to otherwireless APs, for example, other APs in its ESS, that indicates that thetime and frequency resources of the TXOP can be shared by the wirelesscommunication device 1100. After transmitting the CTI frame, the TX/RXmodule 1108 may receive a CTR frame from each of one or more candidateAPs that includes a power indication, for example, an RX power or RSSImeasured by the respective AP, and that indicates a desire by therespective AP to participate in the TXOP. For example, the TX/RX module1108 may be configured to perform blocks 808 and 810 of the process 800described with reference to FIG. 8. The candidate selection module 1104may select one or more of the candidate APs to participate in the TXOPbased on the received power indications and based on the TX power thewireless communication device 1100 intends to use for transmissionsduring the TXOP.

Based on its own intended TX power, the acceptable SIR at its associatedSTAs, and the received power indications, the TX power determinationmodule 1108 may then calculate or otherwise determine, for example,using Equation 5, the maximum TX power for each of the selected APs touse during the data transmission phase of the TXOP. In someimplementations in which not all of the time or frequency resources ofthe data transmission phase are made available to each of the selectedAPs, the resource allocation module 1110 is configured to determine thetime and frequency resources of the TXOP to allocate to each of theselected APs.

The TX/RX module 1112 is configured to generate and transmit a CTASframe to the selected APs that includes, for each of the selected APs,an indication of the available time and frequency resources usable bythe selected APs to transmit data to, or receive data from, one or morerespective STAs associated with the respective AP during the datatransmission phase of the TXOP. After transmitting the CTAS frame, theTX/RX module 1112 may transmit a CTLS frame to one or more associatedSTAs in its BSS identifying the time and frequency resources availablefor use by itself and its associated BSS. For example, the TX/RX module1108 may be configured to perform block 608 of the process 600 andblocks 902 and 904 of the process 900 described with reference to FIGS.6-9.

In some implementations, in a beginning portion of a data transmissionphase, the TX/RX module 1112 transmits a CTTRIG frame to the selectedAPs to synchronize in time the selected APs with the wirelesscommunication device 1100. The TX/RX module 1112 may then transmit orreceive one or more DL or UL data communications to or from one or moreSTAs in its BSS using the available time and frequency resources it hasallocated to itself. For example, the TX/RX module 1112 may transmit orreceive data communications including data frames to or from multipleSTAs using MU OFDMA, MU MIMO, or SU techniques. For example, the TX/RXmodule 1112 may be configured to perform block 610 of the process 600described with reference to FIGS. 6-9.

The TX/RX module 1112 is further configured to receive a CTI frame fromanother AP that has obtained a TXOP (TXOP owner) that indicates thatmultiple time and frequency resources of the TXOP can be shared by theTXOP owner. The TX/RX module 1112 is further configured to transmit aCTR frame to the TXOP owner that includes a power indication, such as anindication of an RX power of a received CTS frame, and that generallyindicates a desire to participate in the TXOP. For example, the TX/RXmodule 1112 may be configured to perform block 1006 of the process 1000described with reference to FIG. 10. The TX/RX module 1112 is furtherconfigured to receive a CTAS frame from the TXOP owner that includes anindication of the time and frequency resources of the TXOP that areavailable to the wireless communication device 1100 and that are usableto transmit data to, or receive data from, one or more STAs associatedwith the wireless communication device 1100 during the data transmissionphase of the TXOP. As described above, the CTAS frame may furtherinclude an indication of the maximum TX power usable by AP2 to transmitdata to, or receive data from, one or more respective associated STAsduring the data transmission phase 708 via the indicated time andfrequency resources. For example, the TX/RX module 1112 may beconfigured to perform block 1008 of the process 1000 described withreference to FIG. 10.

As described above, the CTAS frame may include a user information fieldfor the wireless communication device 1100 that includes a value thatexplicitly indicates the maximum TX power for the wireless communicationdevice 1100. Additionally or alternatively, in some implementations, theuser information field provides an implicit indication of the maximum TXpower. For example, the user information field may include an indicationof the maximum TX power in the form of, for example, an indication ofthe TX power of the TXOP owner, an indication of the TXOP owner'smeasurement of the RX power of the CTS frame, and an indication of theSIR. In such examples, the TX power determination module 1108 maycalculate or otherwise determine the maximum transmit power it ispermitted to use based on the indications of the TX power of the TXOPowner, the indication of the TXOP owner's measurement of the RX power ofthe CTS frame and the SIR, based on its own measured RX power of the CTSframe, and based on Equation 5.

The TX/RX module 1112 may then transmit data to, or receive data from,one or more of its associated STAs using the available time andfrequency resources at a TX power at or below the maximum TX power. Forexample, the TX/RX module 1112 may be configured to perform block 1010of the process 1000.

As used herein, “or” is used intended to be interpreted in the inclusivesense, unless otherwise explicitly indicated. For example, “a or b” mayinclude a only, b only, or a combination of a and b. As used herein, aphrase referring to “at least one of” or “one or more of” a list ofitems refers to any combination of those items, including singlemembers. For example, “at least one of: a, b, or c” is intended to coverthe possibilities of: a only, b only, c only, a combination of a and b,a combination of a and c, a combination of b and c, and a combination ofa and b and c.

The various illustrative components, logic, logical blocks, modules,circuits, operations and algorithm processes described in connectionwith the implementations disclosed herein may be implemented aselectronic hardware, firmware, software, or combinations of hardware,firmware or software, including the structures disclosed in thisspecification and the structural equivalents thereof. Theinterchangeability of hardware, firmware and software has been describedgenerally, in terms of functionality, and illustrated in the variousillustrative components, blocks, modules, circuits and processesdescribed above. Whether such functionality is implemented in hardware,firmware or software depends upon the particular application and designconstraints imposed on the overall system.

Various modifications to the implementations described in thisdisclosure may be readily apparent to persons having ordinary skill inthe art, and the generic principles defined herein may be applied toother implementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Additionally, various features that are described in this specificationin the context of separate implementations also can be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation also can beimplemented in multiple implementations separately or in any suitablesubcombination. As such, although features may be described above asacting in particular combinations, and even initially claimed as such,one or more features from a claimed combination can in some cases beexcised from the combination, and the claimed combination may bedirected to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one or moreexample processes in the form of a flowchart or flow diagram. However,other operations that are not depicted can be incorporated in theexample processes that are schematically illustrated. For example, oneor more additional operations can be performed before, after,simultaneously, or between any of the illustrated operations. In somecircumstances, multitasking and parallel processing may be advantageous.Moreover, the separation of various system components in theimplementations described above should not be understood as requiringsuch separation in all implementations, and it should be understood thatthe described program components and systems can generally be integratedtogether in a single software product or packaged into multiple softwareproducts.

What is claimed is:
 1. A method for wireless communication by a firstwireless access point, the method comprising: obtaining a transmissionopportunity for wireless communication via a wireless channel; selectingone or more other wireless access points to participate in thetransmission opportunity; determining a maximum transmit power permittedto be used by each of the one or more selected access points fortransmissions during the transmission opportunity; transmitting amessage to the one or more selected access points that includes, foreach of the selected access points: an indication of time and frequencyresources of the transmission opportunity usable by the selected accesspoint to transmit data to, or receive data from, one or more wirelessstations associated with the selected access point during thetransmission opportunity, and an indication of the maximum transmitpower for the selected access point; and transmitting data to, orreceiving data from, one or more first wireless stations associated withthe first wireless access point using time and frequency resources ofthe transmission opportunity.
 2. The method of claim 1, furthercomprising: transmitting a first frame to at least one station of thefirst wireless stations associated with the first wireless access point;and receiving a second frame from each of one or more candidate accesspoints including the one or more selected access points aftertransmitting the first frame, each second frame including a powerindication, wherein the one or more selected access points are selectedfrom the one or more candidate access points based on the powerindications, and wherein the maximum transmit power for each of the oneor more selected access points is based on the power indication receivedfrom the respective access point.
 3. The method of claim 2, wherein thefirst frame is a request-to-send (RTS) frame and wherein the powerindications are based on respective measurements of a received power ofa clear-to-send (CTS) frame transmitted by the at least one stationassociated with the first wireless access point in response to receivingthe RTS frame.
 4. The method of claim 3, further comprising: receivingthe CTS frame; and determining a power of the CTS frame received by thefirst wireless access point, wherein the determinations of the maximumtransmit powers are based on the received power of the CTS frame.
 5. Themethod of claim 1, wherein the indication of the respective maximumtransmit power for each of the selected access points includes asignal-to-interference ratio threshold, and wherein the message furtherincludes a received power of a clear-to-send (CTS) frame measured by thefirst wireless access point, and a transmit power selected by the firstwireless access point for transmissions by the first wireless accesspoint during the transmission opportunity.
 6. The method of claim 1,further comprising transmitting a second message to the one or morefirst wireless stations that includes an indication of a maximumtransmit power permitted to be used by the first wireless stationsduring the transmission opportunity, wherein the message includes atleast one trigger frame configured to trigger the selected access pointsto transmit, simultaneously with the transmission of the second messageby the first wireless access point, respective second messages to theirrespective basis service sets (BSSs) identifying the maximum transmitpower permitted to be used by the respective wireless stations duringthe transmission opportunity.
 7. The method of claim 6, wherein the atleast one trigger frame includes a user information field for each ofthe selected access points that includes the indication of the maximumtransmit power permitted to be used by the respective access point. 8.The method of claim 6, wherein each of the second messages transmittedby the first wireless access point and the selected access pointsincludes: an indication of time and frequency resources that can be usedby wireless stations associated with the respective access points duringthe transmission opportunity; and an information element (IE) for eachof the first wireless access point and the selected access points thatincludes, for the respective access point, the maximum transmit power.9. A wireless communication device comprising: at least one modem; atleast one processor communicatively coupled with the at least one modem;and at least one memory communicatively coupled with the at least oneprocessor and storing processor-readable code that, when executed by theat least one processor in conjunction with the at least one modem, isconfigured to: obtain a transmission opportunity for wirelesscommunication via a wireless channel; select one or more other wirelessaccess points to participate in the transmission opportunity; determinea maximum transmit power permitted to be used by each of the one or moreselected access points for transmissions during the transmissionopportunity; transmit a message to the one or more selected accesspoints that includes, for each of the selected access points: anindication of time and frequency resources of the transmissionopportunity usable by the selected access point to transmit data to, orreceive data from, one or more wireless stations associated with theselected access point during the transmission opportunity, and anindication of the maximum transmit power for the selected access point;and transmit data to, or receiving data from, one or more first wirelessstations associated with the first wireless access point using time andfrequency resources of the transmission opportunity.
 10. The wirelesscommunication device of claim 9, further comprising: transmitting afirst frame to at least one station of the first wireless stationsassociated with the first wireless access point; and receiving a secondframe from each of one or more candidate access points including the oneor more selected access points after transmitting the first frame, eachsecond frame including a power indication, wherein the one or moreselected access points are selected from the one or more candidateaccess points based on the power indications, and wherein the maximumtransmit power for each of the one or more selected access points isbased on the power indication received from the respective access point.11. The wireless communication device of claim 10, wherein the firstframe is a request-to-send (RTS) frame and wherein the power indicationsare based on respective measurements of a received power of aclear-to-send (CTS) frame transmitted by the at least one stationassociated with the first wireless access point in response to receivingthe RTS frame.
 12. The wireless communication device of claim 11,further comprising: receiving the CTS frame; and determining a power ofthe CTS frame received by the first wireless access point, wherein thedeterminations of the maximum transmit powers are based on the receivedpower of the CTS frame.
 13. The wireless communication device of claim9, wherein the indication of the respective maximum transmit power foreach of the selected access points includes a signal-to-interferenceratio threshold, and wherein the message further includes a receivedpower of a clear-to-send (CTS) frame measured by the first wirelessaccess point, and a transmit power selected by the first wireless accesspoint for transmissions by the first wireless access point during thetransmission opportunity.
 14. The wireless communication device of claim9, further comprising transmitting a second message to the one or morefirst wireless stations that includes an indication of a maximumtransmit power permitted to be used by the first wireless stationsduring the transmission opportunity, wherein the message includes atleast one trigger frame configured to trigger the selected access pointsto transmit, simultaneously with the transmission of the second messageby the first wireless access point, respective second messages to theirrespective basis service sets (BSSs) identifying the maximum transmitpower permitted to be used by the respective wireless stations duringthe transmission opportunity.
 15. The wireless communication device ofclaim 14, wherein the at least one trigger frame includes a userinformation field for each of the selected access points that includesthe indication of the maximum transmit power permitted to be used by therespective access point.
 16. The wireless communication device of claim14, wherein each of the second messages transmitted by the firstwireless access point and the selected access points includes: anindication of time and frequency resources that can be used by wirelessstations associated with the respective access points during thetransmission opportunity; and an information element (IE) for each ofthe first wireless access point and the selected access points thatincludes, for the respective access point, the maximum transmit power.